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	$231.88	9.783%	$254.5648	$254.56	$254.55	$254.60
Purchase #2	$153.56	9.717%	$168.4814	$168.48	$168.50	$168.50
Purchase #3	$88.61	8.865%	$96.4653	$96.47	$96.45	$96.50
Purchase #4	$48.71	11.190%	$54.1606	$54.16	$54.15	$54.20
Purchase #5	$142.62	6.180%	$151.4339	$151.43	$151.45	$151.40
Purchase #6	$241.68	13.804%	$275.0415	$275.04	$275.05	$275.00
Purchase #7	$109.48	7.224%	$117.3888	$117.39	$117.40	$117.40
7 purchase totals =	$1,016.54		$1,117.5363	$1,117.53	$1,117.55	$1,117.60