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	$154.96	4.606%	$162.0975	$162.10	$162.10	$162.10
Purchase #2	$130.99	13.654%	$148.8754	$148.88	$148.90	$148.90
Purchase #3	$62.49	7.297%	$67.0499	$67.05	$67.05	$67.00
Purchase #4	$126.66	4.300%	$132.1064	$132.11	$132.10	$132.10
Purchase #5	$144.52	3.852%	$150.0869	$150.09	$150.10	$150.10
Purchase #6	$33.78	8.267%	$36.5726	$36.57	$36.55	$36.60
Purchase #7	$12.31	10.541%	$13.6076	$13.61	$13.60	$13.60
7 purchase totals =	$665.71		$710.3963	$710.41	$710.40	$710.40