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 $88.74   7.717%   $95.5881   $95.59   $95.60   $95.60  
  Purchase #2 $39.82   11.463%   $44.3846   $44.38   $44.40   $44.40  
  Purchase #3 $123.89   5.707%   $130.9604   $130.96   $130.95   $131.00  
  Purchase #4 $228.57   10.581%   $252.755   $252.76   $252.75   $252.80  
  Purchase #5 $99.71   9.772%   $109.4537   $109.45   $109.45   $109.50  
  Purchase #6 $158.65   11.134%   $176.3141   $176.31   $176.30   $176.30  
  Purchase #7 $182.94   12.477%   $205.7654   $205.77   $205.75   $205.80  
  7 purchase totals = $922.32       $1,015.2213   $1,015.22   $1,015.20   $1,015.40