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	$194.94	10.520%	$215.4477	$215.45	$215.45	$215.40
Purchase #2	$73.52	8.160%	$79.5192	$79.52	$79.50	$79.50
Purchase #3	$172.70	6.551%	$184.0136	$184.01	$184.00	$184.00
Purchase #4	$199.85	9.712%	$219.2594	$219.26	$219.25	$219.30
Purchase #5	$159.89	3.807%	$165.977	$165.98	$166.00	$166.00
Purchase #6	$123.36	3.525%	$127.7084	$127.71	$127.70	$127.70
Purchase #7	$72.34	13.583%	$82.1659	$82.17	$82.15	$82.20
7 purchase totals =	$996.60		$1,074.0912	$1,074.10	$1,074.05	$1,074.10