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	$30.92	5.132%	$32.5068	$32.51	$32.50	$32.50
Purchase #2	$82.56	13.134%	$93.4034	$93.40	$93.40	$93.40
Purchase #3	$66.42	5.237%	$69.8984	$69.90	$69.90	$69.90
Purchase #4	$30.52	6.640%	$32.5465	$32.55	$32.55	$32.50
Purchase #5	$158.90	4.407%	$165.9027	$165.90	$165.90	$165.90
Purchase #6	$250.94	13.859%	$285.7178	$285.72	$285.70	$285.70
Purchase #7	$147.84	12.491%	$166.3067	$166.31	$166.30	$166.30
7 purchase totals =	$768.10		$846.2823	$846.29	$846.25	$846.20