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	$143.84	13.135%	$162.7334	$162.73	$162.75	$162.70
Purchase #2	$244.60	13.556%	$277.758	$277.76	$277.75	$277.80
Purchase #3	$53.93	10.249%	$59.4573	$59.46	$59.45	$59.50
Purchase #4	$117.33	8.378%	$127.1599	$127.16	$127.15	$127.20
Purchase #5	$98.48	13.344%	$111.6212	$111.62	$111.60	$111.60
Purchase #6	$9.42	4.369%	$9.8316	$9.83	$9.85	$9.80
Purchase #7	$238.76	9.377%	$261.1485	$261.15	$261.15	$261.10
7 purchase totals =	$906.36		$1,009.7099	$1,009.71	$1,009.70	$1,009.70