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 $81.27   8.246%   $87.9715   $87.97   $87.95   $88.00  
  Purchase #2 $23.34   12.298%   $26.2104   $26.21   $26.20   $26.20  
  Purchase #3 $78.92   12.211%   $88.5569   $88.56   $88.55   $88.60  
  Purchase #4 $216.65   5.592%   $228.7651   $228.77   $228.75   $228.80  
  Purchase #5 $210.33   5.226%   $221.3218   $221.32   $221.30   $221.30  
  Purchase #6 $228.92   5.437%   $241.3664   $241.37   $241.35   $241.40  
  Purchase #7 $218.37   5.533%   $230.4524   $230.45   $230.45   $230.50  
  7 purchase totals = $1,057.80       $1,124.6445   $1,124.65   $1,124.55   $1,124.80