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	$59.25	13.271%	$67.1131	$67.11	$67.10	$67.10
Purchase #2	$190.58	4.363%	$198.895	$198.90	$198.90	$198.90
Purchase #3	$135.34	13.410%	$153.4891	$153.49	$153.50	$153.50
Purchase #4	$85.28	6.840%	$91.1132	$91.11	$91.10	$91.10
Purchase #5	$159.39	8.345%	$172.6911	$172.69	$172.70	$172.70
Purchase #6	$177.62	5.782%	$187.89	$187.89	$187.90	$187.90
Purchase #7	$152.87	4.333%	$159.4939	$159.49	$159.50	$159.50
7 purchase totals =	$960.33		$1,030.6854	$1,030.68	$1,030.70	$1,030.70