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	$53.73	10.665%	$59.4603	$59.46	$59.45	$59.50
Purchase #2	$45.96	5.835%	$48.6418	$48.64	$48.65	$48.60
Purchase #3	$10.94	9.320%	$11.9596	$11.96	$11.95	$12.00
Purchase #4	$106.47	6.831%	$113.743	$113.74	$113.75	$113.70
Purchase #5	$27.26	3.650%	$28.255	$28.26	$28.25	$28.30
Purchase #6	$95.63	9.223%	$104.45	$104.45	$104.45	$104.50
Purchase #7	$94.39	6.546%	$100.5688	$100.57	$100.55	$100.60
7 purchase totals =	$434.38		$467.0785	$467.08	$467.05	$467.20