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	$173.97	12.445%	$195.6206	$195.62	$195.60	$195.60
Purchase #2	$222.36	8.247%	$240.698	$240.70	$240.70	$240.70
Purchase #3	$176.61	11.306%	$196.5775	$196.58	$196.60	$196.60
Purchase #4	$64.28	10.511%	$71.0365	$71.04	$71.05	$71.00
Purchase #5	$164.73	8.354%	$178.4915	$178.49	$178.50	$178.50
Purchase #6	$147.39	12.199%	$165.3701	$165.37	$165.35	$165.40
Purchase #7	$113.89	9.858%	$125.1173	$125.12	$125.10	$125.10
7 purchase totals =	$1,063.23		$1,172.9115	$1,172.92	$1,172.90	$1,172.90