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	$57.42	4.139%	$59.7966	$59.80	$59.80	$59.80
Purchase #2	$140.29	3.258%	$144.8606	$144.86	$144.85	$144.90
Purchase #3	$186.92	3.611%	$193.6697	$193.67	$193.65	$193.70
Purchase #4	$86.49	13.468%	$98.1385	$98.14	$98.15	$98.10
Purchase #5	$62.78	6.251%	$66.7044	$66.70	$66.70	$66.70
Purchase #6	$248.26	11.541%	$276.9117	$276.91	$276.90	$276.90
Purchase #7	$209.43	6.182%	$222.377	$222.38	$222.40	$222.40
7 purchase totals =	$991.59		$1,062.4585	$1,062.46	$1,062.45	$1,062.50