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	$175.84	4.269%	$183.3466	$183.35	$183.35	$183.30
Purchase #2	$23.42	3.465%	$24.2315	$24.23	$24.25	$24.20
Purchase #3	$225.57	5.341%	$237.6177	$237.62	$237.60	$237.60
Purchase #4	$78.83	13.591%	$89.5438	$89.54	$89.55	$89.50
Purchase #5	$53.54	5.698%	$56.5907	$56.59	$56.60	$56.60
Purchase #6	$139.39	10.698%	$154.3019	$154.30	$154.30	$154.30
Purchase #7	$206.81	4.417%	$215.9448	$215.94	$215.95	$215.90
7 purchase totals =	$903.40		$961.5770	$961.57	$961.60	$961.40