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	$97.40	4.403%	$101.6885	$101.69	$101.70	$101.70
Purchase #2	$210.76	9.834%	$231.4861	$231.49	$231.50	$231.50
Purchase #3	$214.26	12.304%	$240.6226	$240.62	$240.60	$240.60
Purchase #4	$78.75	6.385%	$83.7782	$83.78	$83.80	$83.80
Purchase #5	$105.96	7.635%	$114.05	$114.05	$114.05	$114.10
Purchase #6	$143.40	8.513%	$155.6076	$155.61	$155.60	$155.60
Purchase #7	$44.90	13.444%	$50.9364	$50.94	$50.95	$50.90
7 purchase totals =	$895.43		$978.1694	$978.18	$978.20	$978.20