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	$243.75	9.694%	$267.3791	$267.38	$267.40	$267.40
Purchase #2	$227.53	12.111%	$255.0862	$255.09	$255.10	$255.10
Purchase #3	$103.79	3.555%	$107.4797	$107.48	$107.50	$107.50
Purchase #4	$94.42	7.379%	$101.3873	$101.39	$101.40	$101.40
Purchase #5	$77.40	4.329%	$80.7506	$80.75	$80.75	$80.80
Purchase #6	$116.50	11.164%	$129.5061	$129.51	$129.50	$129.50
Purchase #7	$102.38	8.653%	$111.2389	$111.24	$111.25	$111.20
7 purchase totals =	$965.77		$1,052.8279	$1,052.84	$1,052.90	$1,052.90