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	$197.66	7.303%	$212.0951	$212.10	$212.10	$212.10
Purchase #2	$154.73	11.630%	$172.7251	$172.73	$172.75	$172.70
Purchase #3	$29.87	8.223%	$32.3262	$32.33	$32.35	$32.30
Purchase #4	$139.47	12.192%	$156.4742	$156.47	$156.45	$156.50
Purchase #5	$207.91	8.538%	$225.6614	$225.66	$225.65	$225.70
Purchase #6	$49.82	8.673%	$54.1409	$54.14	$54.15	$54.10
Purchase #7	$134.45	10.717%	$148.859	$148.86	$148.85	$148.90
7 purchase totals =	$913.91		$1,002.2819	$1,002.29	$1,002.30	$1,002.30