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 $43.96   10.619%   $48.6281   $48.63   $48.65   $48.60  
  Purchase #2 $200.80   8.741%   $218.3519   $218.35   $218.35   $218.40  
  Purchase #3 $78.99   11.155%   $87.8013   $87.80   $87.80   $87.80  
  Purchase #4 $158.45   4.298%   $165.2602   $165.26   $165.25   $165.30  
  Purchase #5 $169.80   13.322%   $192.4208   $192.42   $192.40   $192.40  
  Purchase #6 $179.41   13.419%   $203.485   $203.49   $203.50   $203.50  
  Purchase #7 $120.26   4.787%   $126.0168   $126.02   $126.00   $126.00  
  7 purchase totals = $951.67       $1,041.9641   $1,041.97   $1,041.95   $1,042.00