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	$67.53	9.431%	$73.8988	$73.90	$73.90	$73.90
Purchase #2	$183.82	8.869%	$200.123	$200.12	$200.10	$200.10
Purchase #3	$45.69	4.639%	$47.8096	$47.81	$47.80	$47.80
Purchase #4	$204.46	6.843%	$218.4512	$218.45	$218.45	$218.50
Purchase #5	$185.61	8.231%	$200.8876	$200.89	$200.90	$200.90
Purchase #6	$122.46	8.163%	$132.4564	$132.46	$132.45	$132.50
Purchase #7	$97.78	4.181%	$101.8682	$101.87	$101.85	$101.90
7 purchase totals =	$907.35		$975.4948	$975.50	$975.45	$975.60