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	$160.48	11.804%	$179.4231	$179.42	$179.40	$179.40
Purchase #2	$43.63	12.559%	$49.1095	$49.11	$49.10	$49.10
Purchase #3	$98.49	13.154%	$111.4454	$111.45	$111.45	$111.40
Purchase #4	$88.59	10.252%	$97.6722	$97.67	$97.65	$97.70
Purchase #5	$29.29	10.182%	$32.2723	$32.27	$32.25	$32.30
Purchase #6	$31.33	4.820%	$32.8401	$32.84	$32.85	$32.80
Purchase #7	$202.56	8.805%	$220.3954	$220.40	$220.40	$220.40
7 purchase totals =	$654.37		$723.1580	$723.16	$723.10	$723.10