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	$107.80	3.761%	$111.8544	$111.85	$111.85	$111.90
Purchase #2	$209.40	3.679%	$217.1038	$217.10	$217.10	$217.10
Purchase #3	$191.92	13.695%	$218.2034	$218.20	$218.20	$218.20
Purchase #4	$126.89	4.856%	$133.0518	$133.05	$133.05	$133.10
Purchase #5	$133.39	5.527%	$140.7625	$140.76	$140.75	$140.80
Purchase #6	$48.95	9.597%	$53.6477	$53.65	$53.65	$53.60
Purchase #7	$53.69	10.745%	$59.459	$59.46	$59.45	$59.50
7 purchase totals =	$872.04		$934.0826	$934.07	$934.05	$934.20