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	$213.85	11.377%	$238.1797	$238.18	$238.20	$238.20
Purchase #2	$51.98	4.434%	$54.2848	$54.28	$54.30	$54.30
Purchase #3	$243.73	10.421%	$269.1291	$269.13	$269.15	$269.10
Purchase #4	$92.64	7.515%	$99.6019	$99.60	$99.60	$99.60
Purchase #5	$140.78	9.174%	$153.6952	$153.70	$153.70	$153.70
Purchase #6	$133.65	9.527%	$146.3828	$146.38	$146.40	$146.40
Purchase #7	$250.53	5.513%	$264.3417	$264.34	$264.35	$264.30
7 purchase totals =	$1,127.16		$1,225.6152	$1,225.61	$1,225.70	$1,225.60