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	$11.54	11.575%	$12.8758	$12.88	$12.90	$12.90
Purchase #2	$206.72	11.814%	$231.1419	$231.14	$231.15	$231.10
Purchase #3	$126.39	5.601%	$133.4691	$133.47	$133.45	$133.50
Purchase #4	$104.65	6.439%	$111.3884	$111.39	$111.40	$111.40
Purchase #5	$39.51	6.411%	$42.043	$42.04	$42.05	$42.00
Purchase #6	$242.53	6.819%	$259.0681	$259.07	$259.05	$259.10
Purchase #7	$222.48	10.244%	$245.2709	$245.27	$245.25	$245.30
7 purchase totals =	$953.82		$1,035.2572	$1,035.26	$1,035.25	$1,035.30