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	$219.71	9.265%	$240.0661	$240.07	$240.05	$240.10
Purchase #2	$90.42	9.829%	$99.3074	$99.31	$99.30	$99.30
Purchase #3	$249.26	10.325%	$274.9961	$275.00	$275.00	$275.00
Purchase #4	$129.49	7.853%	$139.6588	$139.66	$139.65	$139.70
Purchase #5	$59.59	5.602%	$62.9282	$62.93	$62.95	$62.90
Purchase #6	$61.78	4.309%	$64.4421	$64.44	$64.45	$64.40
Purchase #7	$21.89	7.148%	$23.4547	$23.45	$23.45	$23.50
7 purchase totals =	$832.14		$904.8534	$904.86	$904.85	$904.90