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	$138.51	12.805%	$156.2462	$156.25	$156.25	$156.20
Purchase #2	$173.51	13.378%	$196.7222	$196.72	$196.70	$196.70
Purchase #3	$161.53	13.621%	$183.532	$183.53	$183.55	$183.50
Purchase #4	$52.29	5.264%	$55.0425	$55.04	$55.05	$55.00
Purchase #5	$158.41	13.105%	$179.1696	$179.17	$179.15	$179.20
Purchase #6	$148.48	5.240%	$156.2604	$156.26	$156.25	$156.30
Purchase #7	$120.55	3.836%	$125.1743	$125.17	$125.15	$125.20
7 purchase totals =	$953.28		$1,052.1472	$1,052.14	$1,052.10	$1,052.10