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	$212.54	4.121%	$221.2988	$221.30	$221.30	$221.30
Purchase #2	$97.73	10.540%	$108.0307	$108.03	$108.05	$108.00
Purchase #3	$194.53	10.130%	$214.2359	$214.24	$214.25	$214.20
Purchase #4	$74.89	13.573%	$85.0548	$85.05	$85.05	$85.10
Purchase #5	$61.48	7.156%	$65.8795	$65.88	$65.90	$65.90
Purchase #6	$53.27	11.404%	$59.3449	$59.34	$59.35	$59.30
Purchase #7	$16.91	8.274%	$18.3091	$18.31	$18.30	$18.30
7 purchase totals =	$711.35		$772.1537	$772.15	$772.20	$772.10