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	$127.33	4.685%	$133.2954	$133.30	$133.30	$133.30
Purchase #2	$48.62	10.617%	$53.782	$53.78	$53.80	$53.80
Purchase #3	$62.66	7.266%	$67.2129	$67.21	$67.20	$67.20
Purchase #4	$225.60	11.110%	$250.6642	$250.66	$250.65	$250.70
Purchase #5	$19.83	4.503%	$20.7229	$20.72	$20.70	$20.70
Purchase #6	$231.90	5.285%	$244.1559	$244.16	$244.15	$244.20
Purchase #7	$12.55	7.621%	$13.5064	$13.51	$13.50	$13.50
7 purchase totals =	$728.49		$783.3397	$783.34	$783.30	$783.40