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	$211.76	12.464%	$238.1538	$238.15	$238.15	$238.20
Purchase #2	$55.34	8.276%	$59.9199	$59.92	$59.90	$59.90
Purchase #3	$193.75	8.105%	$209.4534	$209.45	$209.45	$209.50
Purchase #4	$41.96	7.687%	$45.1855	$45.19	$45.20	$45.20
Purchase #5	$18.81	4.425%	$19.6423	$19.64	$19.65	$19.60
Purchase #6	$243.77	8.754%	$265.1096	$265.11	$265.10	$265.10
Purchase #7	$185.75	5.449%	$195.8715	$195.87	$195.85	$195.90
7 purchase totals =	$951.14		$1,033.3360	$1,033.33	$1,033.30	$1,033.40