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	$222.52	10.664%	$246.2495	$246.25	$246.25	$246.20
Purchase #2	$216.28	13.810%	$246.1483	$246.15	$246.15	$246.10
Purchase #3	$30.33	7.320%	$32.5502	$32.55	$32.55	$32.60
Purchase #4	$5.44	8.644%	$5.9102	$5.91	$5.90	$5.90
Purchase #5	$94.95	4.617%	$99.3338	$99.33	$99.35	$99.30
Purchase #6	$114.36	13.333%	$129.6076	$129.61	$129.60	$129.60
Purchase #7	$91.83	8.448%	$99.5878	$99.59	$99.60	$99.60
7 purchase totals =	$775.71		$859.3874	$859.39	$859.40	$859.30