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	$166.70	4.451%	$174.1198	$174.12	$174.10	$174.10
Purchase #2	$126.57	10.294%	$139.5991	$139.60	$139.60	$139.60
Purchase #3	$63.77	13.164%	$72.1647	$72.16	$72.15	$72.20
Purchase #4	$58.43	11.485%	$65.1407	$65.14	$65.15	$65.10
Purchase #5	$90.69	8.388%	$98.2971	$98.30	$98.30	$98.30
Purchase #6	$134.62	13.445%	$152.7197	$152.72	$152.70	$152.70
Purchase #7	$196.57	13.595%	$223.2937	$223.29	$223.30	$223.30
7 purchase totals =	$837.35		$925.3348	$925.33	$925.30	$925.30