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	$123.43	6.498%	$131.4505	$131.45	$131.45	$131.50
Purchase #2	$182.25	7.174%	$195.3246	$195.32	$195.30	$195.30
Purchase #3	$193.28	13.539%	$219.4482	$219.45	$219.45	$219.40
Purchase #4	$219.61	10.802%	$243.3323	$243.33	$243.35	$243.30
Purchase #5	$190.81	8.548%	$207.1204	$207.12	$207.10	$207.10
Purchase #6	$166.88	3.251%	$172.3053	$172.31	$172.30	$172.30
Purchase #7	$202.88	9.668%	$222.4944	$222.49	$222.50	$222.50
7 purchase totals =	$1,279.14		$1,391.4757	$1,391.47	$1,391.45	$1,391.40