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 $164.96   6.155%   $175.1133   $175.11   $175.10   $175.10  
  Purchase #2 $91.27   12.243%   $102.4442   $102.44   $102.45   $102.40  
  Purchase #3 $119.89   10.171%   $132.084   $132.08   $132.10   $132.10  
  Purchase #4 $214.69   11.813%   $240.0513   $240.05   $240.05   $240.10  
  Purchase #5 $61.90   13.559%   $70.293   $70.29   $70.30   $70.30  
  Purchase #6 $190.60   6.691%   $203.353   $203.35   $203.35   $203.40  
  Purchase #7 $232.91   4.575%   $243.5656   $243.57   $243.55   $243.60  
  7 purchase totals = $1,076.22       $1,166.9044   $1,166.89   $1,166.90   $1,167.00