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	$197.73	8.395%	$214.3294	$214.33	$214.35	$214.30
Purchase #2	$137.75	10.603%	$152.3556	$152.36	$152.35	$152.40
Purchase #3	$80.36	11.475%	$89.5813	$89.58	$89.60	$89.60
Purchase #4	$14.86	3.823%	$15.4281	$15.43	$15.45	$15.40
Purchase #5	$245.60	7.506%	$264.0347	$264.03	$264.05	$264.00
Purchase #6	$191.86	8.836%	$208.8127	$208.81	$208.80	$208.80
Purchase #7	$227.87	12.220%	$255.7157	$255.72	$255.70	$255.70
7 purchase totals =	$1,096.03		$1,200.2575	$1,200.26	$1,200.30	$1,200.20