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 $167.81   11.283%   $186.744   $186.74   $186.75   $186.70  
  Purchase #2 $89.80   9.353%   $98.199   $98.20   $98.20   $98.20  
  Purchase #3 $161.87   12.348%   $181.8577   $181.86   $181.85   $181.90  
  Purchase #4 $172.63   6.746%   $184.2756   $184.28   $184.30   $184.30  
  Purchase #5 $243.27   6.226%   $258.416   $258.42   $258.40   $258.40  
  Purchase #6 $189.39   9.165%   $206.7476   $206.75   $206.75   $206.70  
  Purchase #7 $196.72   7.247%   $210.9763   $210.98   $211.00   $211.00  
  7 purchase totals = $1,221.49       $1,327.2162   $1,327.23   $1,327.25   $1,327.20