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	$190.80	4.763%	$199.8878	$199.89	$199.90	$199.90
Purchase #2	$133.76	12.698%	$150.7448	$150.74	$150.75	$150.70
Purchase #3	$75.55	4.406%	$78.8787	$78.88	$78.90	$78.90
Purchase #4	$239.95	6.836%	$256.353	$256.35	$256.35	$256.40
Purchase #5	$190.51	13.320%	$215.8859	$215.89	$215.90	$215.90
Purchase #6	$54.45	8.474%	$59.0641	$59.06	$59.05	$59.10
Purchase #7	$66.78	11.747%	$74.6246	$74.62	$74.60	$74.60
7 purchase totals =	$951.80		$1,035.4389	$1,035.43	$1,035.45	$1,035.50