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	$158.40	8.668%	$172.1301	$172.13	$172.15	$172.10
Purchase #2	$28.67	11.536%	$31.9774	$31.98	$32.00	$32.00
Purchase #3	$207.31	4.402%	$216.4358	$216.44	$216.45	$216.40
Purchase #4	$196.53	6.288%	$208.8878	$208.89	$208.90	$208.90
Purchase #5	$242.61	10.114%	$267.1476	$267.15	$267.15	$267.10
Purchase #6	$32.33	7.215%	$34.6626	$34.66	$34.65	$34.70
Purchase #7	$184.86	4.155%	$192.5409	$192.54	$192.55	$192.50
7 purchase totals =	$1,050.71		$1,123.7822	$1,123.79	$1,123.85	$1,123.70