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 $181.95   6.741%   $194.2152   $194.22   $194.20   $194.20  
  Purchase #2 $194.41   4.254%   $202.6802   $202.68   $202.70   $202.70  
  Purchase #3 $175.38   6.222%   $186.2921   $186.29   $186.30   $186.30  
  Purchase #4 $196.94   5.263%   $207.305   $207.31   $207.30   $207.30  
  Purchase #5 $180.80   9.416%   $197.8241   $197.82   $197.80   $197.80  
  Purchase #6 $175.28   9.869%   $192.5784   $192.58   $192.60   $192.60  
  Purchase #7 $191.50   6.681%   $204.2941   $204.29   $204.30   $204.30  
  7 purchase totals = $1,296.26       $1,385.1891   $1,385.19   $1,385.20   $1,385.20