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	$191.86	3.155%	$197.9132	$197.91	$197.90	$197.90
Purchase #2	$141.63	6.854%	$151.3373	$151.34	$151.35	$151.30
Purchase #3	$117.84	8.219%	$127.5253	$127.53	$127.55	$127.50
Purchase #4	$34.40	11.846%	$38.475	$38.48	$38.50	$38.50
Purchase #5	$223.56	7.680%	$240.7294	$240.73	$240.75	$240.70
Purchase #6	$74.70	4.495%	$78.0578	$78.06	$78.05	$78.10
Purchase #7	$195.40	5.340%	$205.8344	$205.83	$205.85	$205.80
7 purchase totals =	$979.39		$1,039.8724	$1,039.88	$1,039.95	$1,039.80