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	$206.74	3.306%	$213.5748	$213.57	$213.55	$213.60
Purchase #2	$95.51	5.227%	$100.5023	$100.50	$100.50	$100.50
Purchase #3	$102.63	13.438%	$116.4214	$116.42	$116.40	$116.40
Purchase #4	$130.36	5.801%	$137.9222	$137.92	$137.90	$137.90
Purchase #5	$10.97	13.545%	$12.4559	$12.46	$12.45	$12.50
Purchase #6	$125.32	12.760%	$141.3108	$141.31	$141.30	$141.30
Purchase #7	$151.85	11.674%	$169.577	$169.58	$169.60	$169.60
7 purchase totals =	$823.38		$891.7644	$891.76	$891.70	$891.80