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 $88.79   7.179%   $95.1642   $95.16   $95.15   $95.20  
  Purchase #2 $218.62   7.295%   $234.5683   $234.57   $234.55   $234.60  
  Purchase #3 $137.52   3.466%   $142.2864   $142.29   $142.30   $142.30  
  Purchase #4 $44.41   12.851%   $50.1171   $50.12   $50.10   $50.10  
  Purchase #5 $135.33   4.787%   $141.8082   $141.81   $141.80   $141.80  
  Purchase #6 $186.58   7.849%   $201.2247   $201.22   $201.20   $201.20  
  Purchase #7 $183.83   11.492%   $204.9557   $204.96   $204.95   $205.00  
  7 purchase totals = $995.08       $1,070.1246   $1,070.13   $1,070.05   $1,070.20