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	$83.70	13.313%	$94.843	$94.84	$94.85	$94.80
Purchase #2	$166.41	3.800%	$172.7336	$172.73	$172.75	$172.70
Purchase #3	$13.68	4.538%	$14.3008	$14.30	$14.30	$14.30
Purchase #4	$41.70	7.648%	$44.8892	$44.89	$44.90	$44.90
Purchase #5	$89.32	11.399%	$99.5016	$99.50	$99.50	$99.50
Purchase #6	$119.76	4.162%	$124.7444	$124.74	$124.75	$124.70
Purchase #7	$176.98	7.201%	$189.7243	$189.72	$189.70	$189.70
7 purchase totals =	$691.55		$740.7369	$740.72	$740.75	$740.60