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	$199.28	11.583%	$222.3626	$222.36	$222.35	$222.40
Purchase #2	$6.56	10.373%	$7.2405	$7.24	$7.25	$7.20
Purchase #3	$171.66	8.191%	$185.7207	$185.72	$185.70	$185.70
Purchase #4	$87.94	13.530%	$99.8383	$99.84	$99.85	$99.80
Purchase #5	$202.71	6.246%	$215.3713	$215.37	$215.35	$215.40
Purchase #6	$142.42	3.231%	$147.0216	$147.02	$147.00	$147.00
Purchase #7	$172.52	6.770%	$184.1996	$184.20	$184.20	$184.20
7 purchase totals =	$983.09		$1,061.7546	$1,061.75	$1,061.70	$1,061.70