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	$223.63	10.568%	$247.2632	$247.26	$247.25	$247.30
Purchase #2	$146.67	9.254%	$160.2428	$160.24	$160.25	$160.20
Purchase #3	$227.50	8.620%	$247.1105	$247.11	$247.10	$247.10
Purchase #4	$33.62	10.779%	$37.2439	$37.24	$37.25	$37.20
Purchase #5	$144.37	10.363%	$159.3311	$159.33	$159.35	$159.30
Purchase #6	$137.50	10.174%	$151.4893	$151.49	$151.50	$151.50
Purchase #7	$160.82	13.121%	$181.9212	$181.92	$181.90	$181.90
7 purchase totals =	$1,074.11		$1,184.6020	$1,184.59	$1,184.60	$1,184.50