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	$52.57	5.397%	$55.4072	$55.41	$55.40	$55.40
Purchase #2	$176.70	11.207%	$196.5028	$196.50	$196.50	$196.50
Purchase #3	$30.71	8.586%	$33.3468	$33.35	$33.35	$33.30
Purchase #4	$16.85	5.591%	$17.7921	$17.79	$17.80	$17.80
Purchase #5	$35.35	11.188%	$39.305	$39.31	$39.30	$39.30
Purchase #6	$247.48	4.771%	$259.2873	$259.29	$259.30	$259.30
Purchase #7	$131.41	11.782%	$146.8927	$146.89	$146.90	$146.90
7 purchase totals =	$691.07		$748.5339	$748.54	$748.55	$748.50