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	$146.90	12.628%	$165.4505	$165.45	$165.45	$165.50
Purchase #2	$67.79	13.412%	$76.882	$76.88	$76.90	$76.90
Purchase #3	$124.42	4.206%	$129.6531	$129.65	$129.65	$129.70
Purchase #4	$44.29	7.137%	$47.451	$47.45	$47.45	$47.50
Purchase #5	$154.64	9.164%	$168.8112	$168.81	$168.80	$168.80
Purchase #6	$53.47	10.632%	$59.1549	$59.15	$59.15	$59.20
Purchase #7	$174.37	11.317%	$194.1035	$194.10	$194.10	$194.10
7 purchase totals =	$765.88		$841.5062	$841.49	$841.50	$841.70