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 $65.83   12.111%   $73.8027   $73.80   $73.80   $73.80  
  Purchase #2 $140.44   7.492%   $150.9618   $150.96   $150.95   $151.00  
  Purchase #3 $216.72   8.747%   $235.6765   $235.68   $235.70   $235.70  
  Purchase #4 $219.99   3.141%   $226.8999   $226.90   $226.90   $226.90  
  Purchase #5 $42.86   6.212%   $45.5225   $45.52   $45.50   $45.50  
  Purchase #6 $147.72   3.424%   $152.7779   $152.78   $152.80   $152.80  
  Purchase #7 $188.32   11.575%   $210.118   $210.12   $210.10   $210.10  
  7 purchase totals = $1,021.88       $1,095.7593   $1,095.76   $1,095.75   $1,095.80