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	$211.65	7.619%	$227.7756	$227.78	$227.80	$227.80
Purchase #2	$101.35	10.428%	$111.9188	$111.92	$111.90	$111.90
Purchase #3	$235.34	6.463%	$250.55	$250.55	$250.55	$250.60
Purchase #4	$12.74	8.690%	$13.8471	$13.85	$13.85	$13.80
Purchase #5	$83.92	6.456%	$89.3379	$89.34	$89.35	$89.30
Purchase #6	$186.87	10.563%	$206.6091	$206.61	$206.60	$206.60
Purchase #7	$205.32	5.713%	$217.0499	$217.05	$217.05	$217.00
7 purchase totals =	$1,037.19		$1,117.0884	$1,117.10	$1,117.10	$1,117.00