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	$69.39	6.413%	$73.84	$73.84	$73.85	$73.80
Purchase #2	$182.55	4.325%	$190.4453	$190.45	$190.45	$190.40
Purchase #3	$68.50	6.441%	$72.9121	$72.91	$72.90	$72.90
Purchase #4	$79.58	11.597%	$88.8089	$88.81	$88.80	$88.80
Purchase #5	$40.45	12.511%	$45.5107	$45.51	$45.50	$45.50
Purchase #6	$50.46	13.658%	$57.3518	$57.35	$57.35	$57.40
Purchase #7	$195.48	4.733%	$204.7321	$204.73	$204.75	$204.70
7 purchase totals =	$686.41		$733.6009	$733.60	$733.60	$733.50