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	$126.78	11.267%	$141.0643	$141.06	$141.05	$141.10
Purchase #2	$246.69	12.661%	$277.9234	$277.92	$277.90	$277.90
Purchase #3	$57.43	5.220%	$60.4278	$60.43	$60.45	$60.40
Purchase #4	$61.72	4.687%	$64.6128	$64.61	$64.60	$64.60
Purchase #5	$30.29	5.465%	$31.9453	$31.95	$31.95	$31.90
Purchase #6	$103.25	7.538%	$111.033	$111.03	$111.05	$111.00
Purchase #7	$32.75	12.135%	$36.7242	$36.72	$36.70	$36.70
7 purchase totals =	$658.91		$723.7308	$723.72	$723.70	$723.60