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	$207.66	3.492%	$214.9115	$214.91	$214.90	$214.90
Purchase #2	$193.36	7.812%	$208.4653	$208.47	$208.45	$208.50
Purchase #3	$242.33	12.111%	$271.6786	$271.68	$271.70	$271.70
Purchase #4	$170.40	12.349%	$191.4427	$191.44	$191.45	$191.40
Purchase #5	$102.54	13.495%	$116.3778	$116.38	$116.40	$116.40
Purchase #6	$172.38	10.678%	$190.7867	$190.79	$190.80	$190.80
Purchase #7	$133.95	4.155%	$139.5156	$139.52	$139.50	$139.50
7 purchase totals =	$1,222.62		$1,333.1782	$1,333.19	$1,333.20	$1,333.20