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	$182.58	5.420%	$192.4758	$192.48	$192.50	$192.50
Purchase #2	$185.60	3.381%	$191.8751	$191.88	$191.90	$191.90
Purchase #3	$58.61	5.636%	$61.9133	$61.91	$61.90	$61.90
Purchase #4	$229.58	11.198%	$255.2884	$255.29	$255.30	$255.30
Purchase #5	$93.70	11.357%	$104.3415	$104.34	$104.35	$104.30
Purchase #6	$239.60	8.862%	$260.8334	$260.83	$260.85	$260.80
Purchase #7	$150.48	3.187%	$155.2758	$155.28	$155.30	$155.30
7 purchase totals =	$1,140.15		$1,222.0033	$1,222.01	$1,222.10	$1,222.00