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	$198.61	11.861%	$222.1671	$222.17	$222.15	$222.20
Purchase #2	$246.95	13.326%	$279.8586	$279.86	$279.85	$279.90
Purchase #3	$182.84	9.118%	$199.5114	$199.51	$199.50	$199.50
Purchase #4	$26.45	11.642%	$29.5293	$29.53	$29.55	$29.50
Purchase #5	$42.82	10.326%	$47.2416	$47.24	$47.25	$47.20
Purchase #6	$78.93	3.456%	$81.6578	$81.66	$81.65	$81.70
Purchase #7	$145.41	11.607%	$162.2877	$162.29	$162.30	$162.30
7 purchase totals =	$922.01		$1,022.2535	$1,022.26	$1,022.25	$1,022.30