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	$158.31	13.137%	$179.1072	$179.11	$179.10	$179.10
Purchase #2	$7.41	6.252%	$7.8733	$7.87	$7.85	$7.90
Purchase #3	$52.89	5.309%	$55.6979	$55.70	$55.70	$55.70
Purchase #4	$129.56	12.716%	$146.0348	$146.03	$146.05	$146.00
Purchase #5	$40.96	4.741%	$42.9019	$42.90	$42.90	$42.90
Purchase #6	$13.62	9.655%	$14.935	$14.94	$14.95	$14.90
Purchase #7	$5.59	8.546%	$6.0677	$6.07	$6.05	$6.10
7 purchase totals =	$408.34		$452.6178	$452.62	$452.60	$452.60