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 $186.48   4.568%   $194.9984   $195.00   $195.00   $195.00  
  Purchase #2 $223.77   12.170%   $251.0028   $251.00   $251.00   $251.00  
  Purchase #3 $99.98   11.612%   $111.5897   $111.59   $111.60   $111.60  
  Purchase #4 $11.67   6.369%   $12.4133   $12.41   $12.40   $12.40  
  Purchase #5 $218.56   3.714%   $226.6773   $226.68   $226.70   $226.70  
  Purchase #6 $147.74   13.817%   $168.1532   $168.15   $168.15   $168.20  
  Purchase #7 $228.49   6.865%   $244.1758   $244.18   $244.20   $244.20  
  7 purchase totals = $1,116.69       $1,209.0105   $1,209.01   $1,209.05   $1,209.10