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	$164.31	9.580%	$180.0509	$180.05	$180.05	$180.10
Purchase #2	$138.92	5.829%	$147.0176	$147.02	$147.00	$147.00
Purchase #3	$7.35	3.498%	$7.6071	$7.61	$7.60	$7.60
Purchase #4	$21.96	13.552%	$24.936	$24.94	$24.95	$24.90
Purchase #5	$247.72	3.671%	$256.8138	$256.81	$256.80	$256.80
Purchase #6	$120.27	9.277%	$131.4274	$131.43	$131.45	$131.40
Purchase #7	$33.96	11.621%	$37.9065	$37.91	$37.90	$37.90
7 purchase totals =	$734.49		$785.7593	$785.77	$785.75	$785.70