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 $246.50   8.569%   $267.6226   $267.62   $267.60   $267.60  
  Purchase #2 $171.59   13.825%   $195.3123   $195.31   $195.30   $195.30  
  Purchase #3 $96.84   11.721%   $108.1906   $108.19   $108.20   $108.20  
  Purchase #4 $219.44   4.740%   $229.8415   $229.84   $229.85   $229.80  
  Purchase #5 $115.35   7.111%   $123.5525   $123.55   $123.55   $123.60  
  Purchase #6 $34.39   9.151%   $37.537   $37.54   $37.55   $37.50  
  Purchase #7 $156.35   10.133%   $172.1929   $172.19   $172.20   $172.20  
  7 purchase totals = $1,040.46       $1,134.2494   $1,134.24   $1,134.25   $1,134.20