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	$188.47	11.645%	$210.4173	$210.42	$210.40	$210.40
Purchase #2	$175.81	13.531%	$199.5989	$199.60	$199.60	$199.60
Purchase #3	$188.75	9.332%	$206.3642	$206.36	$206.35	$206.40
Purchase #4	$41.61	9.391%	$45.5176	$45.52	$45.50	$45.50
Purchase #5	$118.72	9.598%	$130.1147	$130.11	$130.10	$130.10
Purchase #6	$47.34	11.679%	$52.8688	$52.87	$52.85	$52.90
Purchase #7	$46.25	9.378%	$50.5873	$50.59	$50.60	$50.60
7 purchase totals =	$806.95		$895.4688	$895.47	$895.40	$895.50