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 $233.98   3.268%   $241.6265   $241.63   $241.65   $241.60  
  Purchase #2 $77.74   9.768%   $85.3336   $85.33   $85.35   $85.30  
  Purchase #3 $11.30   11.504%   $12.6   $12.60   $12.60   $12.60  
  Purchase #4 $148.83   7.579%   $160.1098   $160.11   $160.10   $160.10  
  Purchase #5 $113.45   7.476%   $121.9315   $121.93   $121.95   $121.90  
  Purchase #6 $189.38   9.144%   $206.6969   $206.70   $206.70   $206.70  
  Purchase #7 $193.31   13.625%   $219.6485   $219.65   $219.65   $219.60  
  7 purchase totals = $967.99       $1,047.9468   $1,047.95   $1,048.00   $1,047.80