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	$171.78	11.545%	$191.612	$191.61	$191.60	$191.60
Purchase #2	$63.48	10.462%	$70.1213	$70.12	$70.10	$70.10
Purchase #3	$142.28	9.608%	$155.9503	$155.95	$155.95	$156.00
Purchase #4	$118.82	10.282%	$131.0371	$131.04	$131.05	$131.00
Purchase #5	$78.59	11.768%	$87.8385	$87.84	$87.85	$87.80
Purchase #6	$124.82	7.724%	$134.4611	$134.46	$134.45	$134.50
Purchase #7	$175.26	9.186%	$191.3594	$191.36	$191.35	$191.40
7 purchase totals =	$875.03		$962.3797	$962.38	$962.35	$962.40