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 $168.86   10.580%   $186.7254   $186.73   $186.75   $186.70  
  Purchase #2 $52.99   4.739%   $55.5012   $55.50   $55.50   $55.50  
  Purchase #3 $212.49   7.414%   $228.244   $228.24   $228.25   $228.20  
  Purchase #4 $21.52   11.855%   $24.0712   $24.07   $24.05   $24.10  
  Purchase #5 $201.31   9.267%   $219.9654   $219.97   $219.95   $220.00  
  Purchase #6 $168.65   4.622%   $176.445   $176.45   $176.45   $176.40  
  Purchase #7 $152.67   12.254%   $171.3782   $171.38   $171.40   $171.40  
  7 purchase totals = $978.49       $1,062.3304   $1,062.34   $1,062.35   $1,062.30