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	$186.85	7.477%	$200.8208	$200.82	$200.80	$200.80
Purchase #2	$67.81	11.272%	$75.4535	$75.45	$75.45	$75.50
Purchase #3	$177.95	7.209%	$190.7784	$190.78	$190.80	$190.80
Purchase #4	$157.25	13.391%	$178.3073	$178.31	$178.30	$178.30
Purchase #5	$173.45	7.672%	$186.7571	$186.76	$186.75	$186.80
Purchase #6	$63.95	11.664%	$71.4091	$71.41	$71.40	$71.40
Purchase #7	$238.42	6.768%	$254.5563	$254.56	$254.55	$254.60
7 purchase totals =	$1,065.68		$1,158.0825	$1,158.09	$1,158.05	$1,158.20