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	$221.81	4.252%	$231.2414	$231.24	$231.25	$231.20
Purchase #2	$243.60	4.438%	$254.411	$254.41	$254.40	$254.40
Purchase #3	$130.71	3.721%	$135.5737	$135.57	$135.55	$135.60
Purchase #4	$93.87	5.521%	$99.0526	$99.05	$99.05	$99.10
Purchase #5	$93.31	12.380%	$104.8618	$104.86	$104.85	$104.90
Purchase #6	$176.48	11.105%	$196.0781	$196.08	$196.10	$196.10
Purchase #7	$114.78	10.111%	$126.3854	$126.39	$126.40	$126.40
7 purchase totals =	$1,074.56		$1,147.6040	$1,147.60	$1,147.60	$1,147.70