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 $91.70   3.611%   $95.0113   $95.01   $95.00   $95.00  
  Purchase #2 $192.47   5.657%   $203.358   $203.36   $203.35   $203.40  
  Purchase #3 $171.27   4.504%   $178.984   $178.98   $179.00   $179.00  
  Purchase #4 $93.73   3.682%   $97.1811   $97.18   $97.20   $97.20  
  Purchase #5 $213.25   13.276%   $241.5611   $241.56   $241.55   $241.60  
  Purchase #6 $36.31   7.290%   $38.957   $38.96   $38.95   $39.00  
  Purchase #7 $193.94   10.368%   $214.0477   $214.05   $214.05   $214.00  
  7 purchase totals = $992.67       $1,069.1002   $1,069.10   $1,069.10   $1,069.20