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	$202.49	11.445%	$225.665	$225.67	$225.65	$225.70
Purchase #2	$85.88	9.800%	$94.2962	$94.30	$94.30	$94.30
Purchase #3	$59.37	5.161%	$62.4341	$62.43	$62.45	$62.40
Purchase #4	$127.41	8.520%	$138.2653	$138.27	$138.25	$138.30
Purchase #5	$16.83	10.797%	$18.6471	$18.65	$18.65	$18.60
Purchase #6	$136.97	10.142%	$150.8615	$150.86	$150.85	$150.90
Purchase #7	$37.56	3.222%	$38.7702	$38.77	$38.75	$38.80
7 purchase totals =	$666.51		$728.9394	$728.95	$728.90	$729.00