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 $81.86   3.459%   $84.6915   $84.69   $84.70   $84.70  
  Purchase #2 $52.77   10.292%   $58.2011   $58.20   $58.20   $58.20  
  Purchase #3 $215.52   12.758%   $243.016   $243.02   $243.00   $243.00  
  Purchase #4 $55.64   9.658%   $61.0137   $61.01   $61.00   $61.00  
  Purchase #5 $118.79   11.613%   $132.5851   $132.59   $132.60   $132.60  
  Purchase #6 $196.82   9.187%   $214.9019   $214.90   $214.90   $214.90  
  Purchase #7 $213.71   6.757%   $228.1504   $228.15   $228.15   $228.20  
  7 purchase totals = $935.11       $1,022.5597   $1,022.56   $1,022.55   $1,022.60