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 $188.37   9.104%   $205.5192   $205.52   $205.50   $205.50  
  Purchase #2 $203.53   3.492%   $210.6373   $210.64   $210.65   $210.60  
  Purchase #3 $148.39   4.623%   $155.2501   $155.25   $155.25   $155.30  
  Purchase #4 $227.59   7.192%   $243.9583   $243.96   $243.95   $244.00  
  Purchase #5 $165.31   7.348%   $177.457   $177.46   $177.45   $177.50  
  Purchase #6 $24.91   6.280%   $26.4743   $26.47   $26.45   $26.50  
  Purchase #7 $163.43   12.163%   $183.308   $183.31   $183.30   $183.30  
  7 purchase totals = $1,121.53       $1,202.6042   $1,202.61   $1,202.55   $1,202.70