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	$166.81	11.175%	$185.451	$185.45	$185.45	$185.50
Purchase #2	$202.71	13.424%	$229.9218	$229.92	$229.90	$229.90
Purchase #3	$250.66	12.498%	$281.9875	$281.99	$282.00	$282.00
Purchase #4	$44.33	4.620%	$46.378	$46.38	$46.40	$46.40
Purchase #5	$42.67	3.670%	$44.236	$44.24	$44.25	$44.20
Purchase #6	$50.29	3.582%	$52.0914	$52.09	$52.10	$52.10
Purchase #7	$41.89	8.695%	$45.5323	$45.53	$45.55	$45.50
7 purchase totals =	$799.36		$885.5980	$885.60	$885.65	$885.60