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	$132.63	3.787%	$137.6527	$137.65	$137.65	$137.70
Purchase #2	$59.41	3.860%	$61.7032	$61.70	$61.70	$61.70
Purchase #3	$113.82	13.117%	$128.7498	$128.75	$128.75	$128.70
Purchase #4	$250.72	7.397%	$269.2658	$269.27	$269.25	$269.30
Purchase #5	$219.40	8.672%	$238.4264	$238.43	$238.45	$238.40
Purchase #6	$83.80	9.351%	$91.6361	$91.64	$91.65	$91.60
Purchase #7	$99.97	11.168%	$111.1346	$111.13	$111.15	$111.10
7 purchase totals =	$959.75		$1,038.5686	$1,038.57	$1,038.60	$1,038.50