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	$178.62	11.827%	$199.7454	$199.75	$199.75	$199.70
Purchase #2	$78.52	6.140%	$83.3411	$83.34	$83.35	$83.30
Purchase #3	$197.48	8.142%	$213.5588	$213.56	$213.55	$213.60
Purchase #4	$108.46	3.119%	$111.8429	$111.84	$111.85	$111.80
Purchase #5	$104.34	7.205%	$111.8577	$111.86	$111.85	$111.90
Purchase #6	$183.72	9.134%	$200.501	$200.50	$200.50	$200.50
Purchase #7	$201.83	4.273%	$210.4542	$210.45	$210.45	$210.50
7 purchase totals =	$1,052.97		$1,131.3011	$1,131.30	$1,131.30	$1,131.30