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	$63.43	12.813%	$71.5573	$71.56	$71.55	$71.60
Purchase #2	$12.73	5.838%	$13.4732	$13.47	$13.45	$13.50
Purchase #3	$195.79	13.642%	$222.4997	$222.50	$222.50	$222.50
Purchase #4	$112.85	9.718%	$123.8168	$123.82	$123.80	$123.80
Purchase #5	$235.64	9.470%	$257.9551	$257.96	$257.95	$258.00
Purchase #6	$44.64	12.172%	$50.0736	$50.07	$50.05	$50.10
Purchase #7	$74.68	11.322%	$83.1353	$83.14	$83.15	$83.10
7 purchase totals =	$739.76		$822.5110	$822.52	$822.45	$822.60