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	$103.57	7.793%	$111.6412	$111.64	$111.65	$111.60
Purchase #2	$187.86	11.339%	$209.1614	$209.16	$209.15	$209.20
Purchase #3	$96.53	8.787%	$105.0121	$105.01	$105.00	$105.00
Purchase #4	$20.34	13.616%	$23.1095	$23.11	$23.10	$23.10
Purchase #5	$122.73	9.268%	$134.1046	$134.10	$134.10	$134.10
Purchase #6	$58.39	13.867%	$66.4869	$66.49	$66.50	$66.50
Purchase #7	$226.34	12.610%	$254.8815	$254.88	$254.90	$254.90
7 purchase totals =	$815.76		$904.3972	$904.39	$904.40	$904.40