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	$234.53	10.105%	$258.2293	$258.23	$258.25	$258.20
Purchase #2	$162.52	10.583%	$179.7195	$179.72	$179.70	$179.70
Purchase #3	$204.70	4.184%	$213.2646	$213.26	$213.25	$213.30
Purchase #4	$89.34	6.657%	$95.2874	$95.29	$95.30	$95.30
Purchase #5	$235.41	6.397%	$250.4692	$250.47	$250.45	$250.50
Purchase #6	$146.89	6.573%	$156.5451	$156.55	$156.55	$156.50
Purchase #7	$48.78	11.585%	$54.4312	$54.43	$54.45	$54.40
7 purchase totals =	$1,122.17		$1,207.9463	$1,207.95	$1,207.95	$1,207.90