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	$76.25	6.765%	$81.4083	$81.41	$81.40	$81.40
Purchase #2	$83.38	6.226%	$88.5712	$88.57	$88.55	$88.60
Purchase #3	$127.83	7.595%	$137.5387	$137.54	$137.55	$137.50
Purchase #4	$191.35	11.446%	$213.2519	$213.25	$213.25	$213.30
Purchase #5	$62.84	7.187%	$67.3563	$67.36	$67.35	$67.40
Purchase #6	$154.64	8.788%	$168.2298	$168.23	$168.25	$168.20
Purchase #7	$168.65	13.569%	$191.5341	$191.53	$191.55	$191.50
7 purchase totals =	$864.94		$947.8903	$947.89	$947.90	$947.90