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	$157.49	11.846%	$176.1463	$176.15	$176.15	$176.10
Purchase #2	$150.57	9.420%	$164.7537	$164.75	$164.75	$164.80
Purchase #3	$231.62	10.467%	$255.8637	$255.86	$255.85	$255.90
Purchase #4	$95.53	11.869%	$106.8685	$106.87	$106.85	$106.90
Purchase #5	$33.54	5.741%	$35.4655	$35.47	$35.45	$35.50
Purchase #6	$232.53	3.461%	$240.5779	$240.58	$240.60	$240.60
Purchase #7	$78.72	3.804%	$81.7145	$81.71	$81.70	$81.70
7 purchase totals =	$980.00		$1,061.3901	$1,061.39	$1,061.35	$1,061.50