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	$184.93	10.758%	$204.8248	$204.82	$204.80	$204.80
Purchase #2	$113.80	12.332%	$127.8338	$127.83	$127.85	$127.80
Purchase #3	$120.86	7.647%	$130.1022	$130.10	$130.10	$130.10
Purchase #4	$47.66	12.178%	$53.464	$53.46	$53.45	$53.50
Purchase #5	$94.31	5.388%	$99.3914	$99.39	$99.40	$99.40
Purchase #6	$37.46	6.401%	$39.8578	$39.86	$39.85	$39.90
Purchase #7	$102.71	8.555%	$111.4968	$111.50	$111.50	$111.50
7 purchase totals =	$701.73		$766.9708	$766.96	$766.95	$767.00