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	$88.70	4.859%	$93.0099	$93.01	$93.00	$93.00
Purchase #2	$63.43	5.112%	$66.6725	$66.67	$66.65	$66.70
Purchase #3	$35.84	3.466%	$37.0822	$37.08	$37.10	$37.10
Purchase #4	$96.48	6.447%	$102.7001	$102.70	$102.70	$102.70
Purchase #5	$45.50	11.526%	$50.7443	$50.74	$50.75	$50.70
Purchase #6	$185.58	5.862%	$196.4587	$196.46	$196.45	$196.50
Purchase #7	$94.30	5.783%	$99.7534	$99.75	$99.75	$99.80
7 purchase totals =	$609.83		$646.4211	$646.41	$646.40	$646.50