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	$96.33	7.389%	$103.4478	$103.45	$103.45	$103.40
Purchase #2	$56.33	7.262%	$60.4207	$60.42	$60.40	$60.40
Purchase #3	$66.34	5.714%	$70.1307	$70.13	$70.15	$70.10
Purchase #4	$170.55	7.162%	$182.7648	$182.76	$182.75	$182.80
Purchase #5	$130.59	8.409%	$141.5713	$141.57	$141.55	$141.60
Purchase #6	$11.72	8.280%	$12.6904	$12.69	$12.70	$12.70
Purchase #7	$185.92	7.517%	$199.8956	$199.90	$199.90	$199.90
7 purchase totals =	$717.78		$770.9213	$770.92	$770.90	$770.90