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	$184.67	7.530%	$198.5757	$198.58	$198.60	$198.60
Purchase #2	$244.70	11.387%	$272.564	$272.56	$272.55	$272.60
Purchase #3	$154.90	10.694%	$171.465	$171.47	$171.45	$171.50
Purchase #4	$60.79	8.449%	$65.9261	$65.93	$65.95	$65.90
Purchase #5	$219.86	5.226%	$231.3499	$231.35	$231.35	$231.30
Purchase #6	$148.80	13.120%	$168.3226	$168.32	$168.30	$168.30
Purchase #7	$82.48	9.559%	$90.3643	$90.36	$90.35	$90.40
7 purchase totals =	$1,096.20		$1,198.5676	$1,198.57	$1,198.55	$1,198.60