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 $59.76   3.584%   $61.9018   $61.90   $61.90   $61.90  
  Purchase #2 $247.85   9.578%   $271.5891   $271.59   $271.60   $271.60  
  Purchase #3 $68.52   9.695%   $75.163   $75.16   $75.15   $75.20  
  Purchase #4 $178.58   5.818%   $188.9698   $188.97   $188.95   $189.00  
  Purchase #5 $138.90   8.449%   $150.6357   $150.64   $150.65   $150.60  
  Purchase #6 $230.37   6.285%   $244.8488   $244.85   $244.85   $244.80  
  Purchase #7 $23.31   11.401%   $25.9676   $25.97   $25.95   $26.00  
  7 purchase totals = $947.29       $1,019.0758   $1,019.08   $1,019.05   $1,019.10