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 $65.60   7.144%   $70.2865   $70.29   $70.30   $70.30  
  Purchase #2 $224.90   11.248%   $250.1968   $250.20   $250.20   $250.20  
  Purchase #3 $219.43   8.425%   $237.917   $237.92   $237.90   $237.90  
  Purchase #4 $216.84   11.407%   $241.5749   $241.57   $241.55   $241.60  
  Purchase #5 $92.50   5.410%   $97.5043   $97.50   $97.50   $97.50  
  Purchase #6 $68.40   9.572%   $74.9472   $74.95   $74.95   $74.90  
  Purchase #7 $38.29   9.539%   $41.9425   $41.94   $41.95   $41.90  
  7 purchase totals = $925.96       $1,014.3692   $1,014.37   $1,014.35   $1,014.30