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	$199.28	11.260%	$221.7189	$221.72	$221.70	$221.70
Purchase #2	$34.42	12.155%	$38.6038	$38.60	$38.60	$38.60
Purchase #3	$154.54	12.474%	$173.8173	$173.82	$173.80	$173.80
Purchase #4	$131.49	4.518%	$137.4307	$137.43	$137.45	$137.40
Purchase #5	$233.54	9.295%	$255.2475	$255.25	$255.25	$255.20
Purchase #6	$114.41	11.286%	$127.3223	$127.32	$127.30	$127.30
Purchase #7	$63.91	8.715%	$69.4798	$69.48	$69.50	$69.50
7 purchase totals =	$931.59		$1,023.6203	$1,023.62	$1,023.60	$1,023.50