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 $88.64   4.873%   $92.9594   $92.96   $92.95   $93.00  
  Purchase #2 $8.97   6.524%   $9.5552   $9.56   $9.55   $9.60  
  Purchase #3 $161.30   6.153%   $171.2248   $171.22   $171.20   $171.20  
  Purchase #4 $175.52   6.793%   $187.4431   $187.44   $187.45   $187.40  
  Purchase #5 $224.66   12.361%   $252.4302   $252.43   $252.45   $252.40  
  Purchase #6 $238.85   11.407%   $266.0956   $266.10   $266.10   $266.10  
  Purchase #7 $145.77   11.726%   $162.863   $162.86   $162.85   $162.90  
  7 purchase totals = $1,043.71       $1,142.5713   $1,142.57   $1,142.55   $1,142.60