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	$105.82	12.106%	$118.6306	$118.63	$118.65	$118.60
Purchase #2	$146.74	13.709%	$166.8566	$166.86	$166.85	$166.90
Purchase #3	$166.63	12.437%	$187.3538	$187.35	$187.35	$187.40
Purchase #4	$55.35	8.352%	$59.9728	$59.97	$59.95	$60.00
Purchase #5	$175.85	13.286%	$199.2134	$199.21	$199.20	$199.20
Purchase #6	$136.88	13.586%	$155.4765	$155.48	$155.50	$155.50
Purchase #7	$90.73	4.155%	$94.4998	$94.50	$94.50	$94.50
7 purchase totals =	$878.00		$982.0035	$982.00	$982.00	$982.10