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	$130.94	11.531%	$146.0387	$146.04	$146.05	$146.00
Purchase #2	$187.41	6.346%	$199.303	$199.30	$199.30	$199.30
Purchase #3	$17.71	12.228%	$19.8756	$19.88	$19.90	$19.90
Purchase #4	$80.27	12.426%	$90.2444	$90.24	$90.25	$90.20
Purchase #5	$199.78	11.228%	$222.2113	$222.21	$222.20	$222.20
Purchase #6	$46.80	8.644%	$50.8454	$50.85	$50.85	$50.80
Purchase #7	$129.51	6.519%	$137.9528	$137.95	$137.95	$138.00
7 purchase totals =	$792.42		$866.4712	$866.47	$866.50	$866.40