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	$63.40	13.218%	$71.7802	$71.78	$71.80	$71.80
Purchase #2	$12.40	5.403%	$13.07	$13.07	$13.05	$13.10
Purchase #3	$89.86	12.438%	$101.0368	$101.04	$101.05	$101.00
Purchase #4	$14.39	7.600%	$15.4836	$15.48	$15.50	$15.50
Purchase #5	$94.26	6.275%	$100.1748	$100.17	$100.15	$100.20
Purchase #6	$117.36	11.123%	$130.414	$130.41	$130.40	$130.40
Purchase #7	$184.68	11.466%	$205.8554	$205.86	$205.85	$205.90
7 purchase totals =	$576.35		$637.8148	$637.81	$637.80	$637.90