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	$92.74	11.628%	$103.5238	$103.52	$103.50	$103.50
Purchase #2	$206.62	7.113%	$221.3169	$221.32	$221.30	$221.30
Purchase #3	$209.26	11.653%	$233.6451	$233.65	$233.65	$233.60
Purchase #4	$207.40	12.663%	$233.6631	$233.66	$233.65	$233.70
Purchase #5	$112.46	5.692%	$118.8612	$118.86	$118.85	$118.90
Purchase #6	$133.49	4.422%	$139.3929	$139.39	$139.40	$139.40
Purchase #7	$133.68	11.373%	$148.8834	$148.88	$148.90	$148.90
7 purchase totals =	$1,095.65		$1,199.2864	$1,199.28	$1,199.25	$1,199.30