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	$209.84	11.129%	$233.1931	$233.19	$233.20	$233.20
Purchase #2	$222.86	13.757%	$253.5189	$253.52	$253.50	$253.50
Purchase #3	$139.46	7.118%	$149.3868	$149.39	$149.40	$149.40
Purchase #4	$232.51	4.822%	$243.7216	$243.72	$243.70	$243.70
Purchase #5	$217.89	9.275%	$238.0993	$238.10	$238.10	$238.10
Purchase #6	$146.42	3.447%	$151.4671	$151.47	$151.45	$151.50
Purchase #7	$115.78	4.436%	$120.916	$120.92	$120.90	$120.90
7 purchase totals =	$1,284.76		$1,390.3028	$1,390.31	$1,390.25	$1,390.30