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	$62.80	4.864%	$65.8546	$65.85	$65.85	$65.90
Purchase #2	$246.81	9.155%	$269.4055	$269.41	$269.40	$269.40
Purchase #3	$132.29	10.703%	$146.449	$146.45	$146.45	$146.40
Purchase #4	$107.98	4.277%	$112.5983	$112.60	$112.60	$112.60
Purchase #5	$212.58	4.530%	$222.2099	$222.21	$222.20	$222.20
Purchase #6	$243.59	4.316%	$254.1033	$254.10	$254.10	$254.10
Purchase #7	$245.51	10.672%	$271.7108	$271.71	$271.70	$271.70
7 purchase totals =	$1,251.56		$1,342.3314	$1,342.33	$1,342.30	$1,342.30