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 $33.98   6.345%   $36.136   $36.14   $36.15   $36.10  
  Purchase #2 $248.76   11.615%   $277.6535   $277.65   $277.65   $277.70  
  Purchase #3 $52.45   7.473%   $56.3696   $56.37   $56.35   $56.40  
  Purchase #4 $232.60   4.253%   $242.4925   $242.49   $242.50   $242.50  
  Purchase #5 $172.41   4.422%   $180.034   $180.03   $180.05   $180.00  
  Purchase #6 $226.85   4.611%   $237.3101   $237.31   $237.30   $237.30  
  Purchase #7 $157.80   7.801%   $170.11   $170.11   $170.10   $170.10  
  7 purchase totals = $1,124.85       $1,200.1057   $1,200.10   $1,200.10   $1,200.10