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	$177.48	8.288%	$192.1895	$192.19	$192.20	$192.20
Purchase #2	$67.44	6.161%	$71.595	$71.60	$71.60	$71.60
Purchase #3	$75.49	4.485%	$78.8757	$78.88	$78.90	$78.90
Purchase #4	$130.83	13.683%	$148.7315	$148.73	$148.75	$148.70
Purchase #5	$37.33	9.370%	$40.8278	$40.83	$40.85	$40.80
Purchase #6	$98.64	13.810%	$112.2622	$112.26	$112.25	$112.30
Purchase #7	$93.76	10.605%	$103.7032	$103.70	$103.70	$103.70
7 purchase totals =	$680.97		$748.1849	$748.19	$748.25	$748.20