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 $216.55   7.528%   $232.8519   $232.85   $232.85   $232.90  
  Purchase #2 $173.80   6.644%   $185.3473   $185.35   $185.35   $185.30  
  Purchase #3 $62.48   5.512%   $65.9239   $65.92   $65.90   $65.90  
  Purchase #4 $64.43   4.633%   $67.415   $67.42   $67.40   $67.40  
  Purchase #5 $196.52   7.652%   $211.5577   $211.56   $211.55   $211.60  
  Purchase #6 $121.93   10.634%   $134.896   $134.90   $134.90   $134.90  
  Purchase #7 $220.94   7.298%   $237.0642   $237.06   $237.05   $237.10  
  7 purchase totals = $1,056.65       $1,135.0560   $1,135.06   $1,135.00   $1,135.10