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 $167.89   9.603%   $184.0125   $184.01   $184.00   $184.00  
  Purchase #2 $170.80   13.305%   $193.5249   $193.52   $193.50   $193.50  
  Purchase #3 $73.75   11.444%   $82.19   $82.19   $82.20   $82.20  
  Purchase #4 $48.31   9.132%   $52.7217   $52.72   $52.70   $52.70  
  Purchase #5 $207.47   9.449%   $227.0738   $227.07   $227.05   $227.10  
  Purchase #6 $99.41   12.600%   $111.9357   $111.94   $111.95   $111.90  
  Purchase #7 $166.36   10.123%   $183.2006   $183.20   $183.20   $183.20  
  7 purchase totals = $933.99       $1,034.6592   $1,034.65   $1,034.60   $1,034.60