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	$191.47	12.726%	$215.8365	$215.84	$215.85	$215.80
Purchase #2	$166.91	3.568%	$172.8653	$172.87	$172.85	$172.90
Purchase #3	$95.70	5.113%	$100.5931	$100.59	$100.60	$100.60
Purchase #4	$231.92	11.282%	$258.0852	$258.09	$258.10	$258.10
Purchase #5	$225.74	6.378%	$240.1377	$240.14	$240.15	$240.10
Purchase #6	$131.73	5.684%	$139.2175	$139.22	$139.20	$139.20
Purchase #7	$61.54	6.541%	$65.5653	$65.57	$65.55	$65.60
7 purchase totals =	$1,105.01		$1,192.3006	$1,192.32	$1,192.30	$1,192.30