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 $194.28   4.346%   $202.7234   $202.72   $202.70   $202.70  
  Purchase #2 $184.37   10.682%   $204.0644   $204.06   $204.05   $204.10  
  Purchase #3 $126.54   3.588%   $131.0803   $131.08   $131.10   $131.10  
  Purchase #4 $185.75   12.146%   $208.3112   $208.31   $208.30   $208.30  
  Purchase #5 $56.30   6.674%   $60.0575   $60.06   $60.05   $60.10  
  Purchase #6 $153.78   11.417%   $171.3371   $171.34   $171.35   $171.30  
  Purchase #7 $79.73   3.629%   $82.6234   $82.62   $82.60   $82.60  
  7 purchase totals = $980.75       $1,060.1973   $1,060.19   $1,060.15   $1,060.20