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	$37.83	10.308%	$41.7295	$41.73	$41.75	$41.70
Purchase #2	$162.61	12.750%	$183.3428	$183.34	$183.35	$183.30
Purchase #3	$79.74	3.869%	$82.8251	$82.83	$82.85	$82.80
Purchase #4	$160.43	6.751%	$171.2606	$171.26	$171.25	$171.30
Purchase #5	$18.85	4.761%	$19.7474	$19.75	$19.75	$19.70
Purchase #6	$140.30	4.164%	$146.1421	$146.14	$146.15	$146.10
Purchase #7	$9.79	5.607%	$10.3389	$10.34	$10.35	$10.30
7 purchase totals =	$609.55		$655.3864	$655.39	$655.45	$655.20