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	$179.45	3.517%	$185.7613	$185.76	$185.75	$185.80
Purchase #2	$219.55	9.737%	$240.9276	$240.93	$240.95	$240.90
Purchase #3	$224.56	8.633%	$243.9463	$243.95	$243.95	$243.90
Purchase #4	$53.54	11.109%	$59.4878	$59.49	$59.50	$59.50
Purchase #5	$73.52	13.565%	$83.493	$83.49	$83.50	$83.50
Purchase #6	$122.65	12.288%	$137.7212	$137.72	$137.70	$137.70
Purchase #7	$69.87	8.603%	$75.8809	$75.88	$75.90	$75.90
7 purchase totals =	$943.14		$1,027.2181	$1,027.22	$1,027.25	$1,027.20