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 $22.59   11.138%   $25.1061   $25.11   $25.10   $25.10  
  Purchase #2 $179.48   7.783%   $193.4489   $193.45   $193.45   $193.40  
  Purchase #3 $202.40   4.557%   $211.6234   $211.62   $211.60   $211.60  
  Purchase #4 $246.81   9.292%   $269.7436   $269.74   $269.75   $269.70  
  Purchase #5 $162.28   4.462%   $169.5209   $169.52   $169.50   $169.50  
  Purchase #6 $154.48   11.322%   $171.9702   $171.97   $171.95   $172.00  
  Purchase #7 $11.80   9.145%   $12.8791   $12.88   $12.90   $12.90  
  7 purchase totals = $979.84       $1,054.2922   $1,054.29   $1,054.25   $1,054.20