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	$147.54	7.367%	$158.4093	$158.41	$158.40	$158.40
Purchase #2	$121.76	6.318%	$129.4528	$129.45	$129.45	$129.50
Purchase #3	$39.72	13.671%	$45.1501	$45.15	$45.15	$45.20
Purchase #4	$137.56	12.329%	$154.5198	$154.52	$154.50	$154.50
Purchase #5	$93.83	12.528%	$105.585	$105.59	$105.60	$105.60
Purchase #6	$130.98	7.555%	$140.8755	$140.88	$140.90	$140.90
Purchase #7	$233.29	3.551%	$241.5741	$241.57	$241.55	$241.60
7 purchase totals =	$904.68		$975.5666	$975.57	$975.55	$975.70