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 $232.73   8.357%   $252.1792   $252.18   $252.20   $252.20  
  Purchase #2 $214.40   7.446%   $230.3642   $230.36   $230.35   $230.40  
  Purchase #3 $54.54   13.635%   $61.9765   $61.98   $62.00   $62.00  
  Purchase #4 $31.91   7.555%   $34.3208   $34.32   $34.30   $34.30  
  Purchase #5 $206.61   10.636%   $228.585   $228.59   $228.60   $228.60  
  Purchase #6 $165.95   6.118%   $176.1028   $176.10   $176.10   $176.10  
  Purchase #7 $156.99   7.752%   $169.1599   $169.16   $169.15   $169.20  
  7 purchase totals = $1,063.13       $1,152.6884   $1,152.69   $1,152.70   $1,152.80