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	$160.84	5.437%	$169.5849	$169.58	$169.60	$169.60
Purchase #2	$223.72	12.739%	$252.2197	$252.22	$252.20	$252.20
Purchase #3	$149.88	8.694%	$162.9106	$162.91	$162.90	$162.90
Purchase #4	$133.57	4.155%	$139.1198	$139.12	$139.10	$139.10
Purchase #5	$173.81	3.838%	$180.4808	$180.48	$180.50	$180.50
Purchase #6	$42.87	12.567%	$48.2575	$48.26	$48.25	$48.30
Purchase #7	$65.83	9.201%	$71.887	$71.89	$71.90	$71.90
7 purchase totals =	$950.52		$1,024.4603	$1,024.46	$1,024.45	$1,024.50