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	$158.68	3.763%	$164.6511	$164.65	$164.65	$164.70
Purchase #2	$104.41	13.319%	$118.3164	$118.32	$118.30	$118.30
Purchase #3	$248.63	13.109%	$281.2229	$281.22	$281.20	$281.20
Purchase #4	$83.78	6.724%	$89.4134	$89.41	$89.40	$89.40
Purchase #5	$87.96	8.396%	$95.3451	$95.35	$95.35	$95.30
Purchase #6	$234.66	5.639%	$247.8925	$247.89	$247.90	$247.90
Purchase #7	$209.36	6.409%	$222.7779	$222.78	$222.80	$222.80
7 purchase totals =	$1,127.48		$1,219.6193	$1,219.62	$1,219.60	$1,219.60