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	$149.49	3.845%	$155.2379	$155.24	$155.25	$155.20
Purchase #2	$124.33	5.164%	$130.7504	$130.75	$130.75	$130.80
Purchase #3	$244.36	7.359%	$262.3425	$262.34	$262.35	$262.30
Purchase #4	$225.82	10.583%	$249.7185	$249.72	$249.70	$249.70
Purchase #5	$222.48	4.218%	$231.8642	$231.86	$231.85	$231.90
Purchase #6	$19.41	10.311%	$21.4114	$21.41	$21.40	$21.40
Purchase #7	$54.26	13.476%	$61.5721	$61.57	$61.55	$61.60
7 purchase totals =	$1,040.15		$1,112.8970	$1,112.89	$1,112.85	$1,112.90