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	$231.78	5.345%	$244.1686	$244.17	$244.15	$244.20
Purchase #2	$56.86	4.782%	$59.579	$59.58	$59.60	$59.60
Purchase #3	$201.82	10.443%	$222.8961	$222.90	$222.90	$222.90
Purchase #4	$135.42	9.782%	$148.6668	$148.67	$148.65	$148.70
Purchase #5	$92.89	12.434%	$104.4399	$104.44	$104.45	$104.40
Purchase #6	$68.78	7.353%	$73.8374	$73.84	$73.85	$73.80
Purchase #7	$81.31	13.355%	$92.169	$92.17	$92.15	$92.20
7 purchase totals =	$868.86		$945.7568	$945.77	$945.75	$945.80