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	$54.91	5.700%	$58.0399	$58.04	$58.05	$58.00
Purchase #2	$216.67	5.185%	$227.9043	$227.90	$227.90	$227.90
Purchase #3	$160.95	7.433%	$172.9134	$172.91	$172.90	$172.90
Purchase #4	$67.39	8.171%	$72.8964	$72.90	$72.90	$72.90
Purchase #5	$23.89	6.613%	$25.4698	$25.47	$25.45	$25.50
Purchase #6	$108.45	3.794%	$112.5646	$112.56	$112.55	$112.60
Purchase #7	$83.40	11.412%	$92.9176	$92.92	$92.90	$92.90
7 purchase totals =	$715.66		$762.7060	$762.70	$762.65	$762.70