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	$58.27	7.302%	$62.5249	$62.52	$62.50	$62.50
Purchase #2	$67.90	6.677%	$72.4337	$72.43	$72.45	$72.40
Purchase #3	$65.35	11.543%	$72.8934	$72.89	$72.90	$72.90
Purchase #4	$21.50	4.723%	$22.5154	$22.52	$22.50	$22.50
Purchase #5	$48.89	11.709%	$54.6145	$54.61	$54.60	$54.60
Purchase #6	$85.71	13.580%	$97.3494	$97.35	$97.35	$97.30
Purchase #7	$233.73	8.758%	$254.2001	$254.20	$254.20	$254.20
7 purchase totals =	$581.35		$636.5314	$636.52	$636.50	$636.40