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	$169.39	8.462%	$183.7238	$183.72	$183.70	$183.70
Purchase #2	$168.48	13.313%	$190.9097	$190.91	$190.90	$190.90
Purchase #3	$182.86	11.332%	$203.5817	$203.58	$203.60	$203.60
Purchase #4	$172.29	7.466%	$185.1532	$185.15	$185.15	$185.20
Purchase #5	$6.39	10.210%	$7.0424	$7.04	$7.05	$7.00
Purchase #6	$146.88	10.624%	$162.4845	$162.48	$162.50	$162.50
Purchase #7	$138.60	8.428%	$150.2812	$150.28	$150.30	$150.30
7 purchase totals =	$984.89		$1,083.1765	$1,083.16	$1,083.20	$1,083.20