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	$52.83	7.806%	$56.9539	$56.95	$56.95	$57.00
Purchase #2	$115.40	3.223%	$119.1193	$119.12	$119.10	$119.10
Purchase #3	$78.45	13.694%	$89.1929	$89.19	$89.20	$89.20
Purchase #4	$226.92	11.571%	$253.1769	$253.18	$253.20	$253.20
Purchase #5	$43.54	4.452%	$45.4784	$45.48	$45.50	$45.50
Purchase #6	$216.34	3.513%	$223.94	$223.94	$223.95	$223.90
Purchase #7	$60.29	10.166%	$66.4191	$66.42	$66.40	$66.40
7 purchase totals =	$793.77		$854.2805	$854.28	$854.30	$854.30