Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $104.35   11.287%   $116.128   $116.13   $116.15   $116.10  
  Purchase #2 $184.28   12.184%   $206.7327   $206.73   $206.75   $206.70  
  Purchase #3 $39.80   10.765%   $44.0845   $44.08   $44.10   $44.10  
  Purchase #4 $172.32   6.456%   $183.445   $183.45   $183.45   $183.40  
  Purchase #5 $119.33   11.510%   $133.0649   $133.06   $133.05   $133.10  
  Purchase #6 $224.44   8.515%   $243.5511   $243.55   $243.55   $243.60  
  Purchase #7 $227.51   10.457%   $251.3007   $251.30   $251.30   $251.30  
  7 purchase totals = $1,072.03       $1,178.3069   $1,178.30   $1,178.35   $1,178.30