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 $235.89   7.364%   $253.2609   $253.26   $253.25   $253.30  
  Purchase #2 $55.96   11.831%   $62.5806   $62.58   $62.60   $62.60  
  Purchase #3 $24.86   4.427%   $25.9606   $25.96   $25.95   $26.00  
  Purchase #4 $150.77   3.256%   $155.6791   $155.68   $155.70   $155.70  
  Purchase #5 $189.82   8.272%   $205.5219   $205.52   $205.50   $205.50  
  Purchase #6 $226.50   7.663%   $243.8567   $243.86   $243.85   $243.90  
  Purchase #7 $143.68   3.458%   $148.6485   $148.65   $148.65   $148.60  
  7 purchase totals = $1,027.48       $1,095.5083   $1,095.51   $1,095.50   $1,095.60