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	$187.33	6.265%	$199.0662	$199.07	$199.05	$199.10
Purchase #2	$245.38	4.686%	$256.8785	$256.88	$256.90	$256.90
Purchase #3	$137.28	8.243%	$148.596	$148.60	$148.60	$148.60
Purchase #4	$37.61	13.818%	$42.8069	$42.81	$42.80	$42.80
Purchase #5	$170.61	10.223%	$188.0515	$188.05	$188.05	$188.10
Purchase #6	$108.29	13.793%	$123.2264	$123.23	$123.25	$123.20
Purchase #7	$86.59	7.178%	$92.8054	$92.81	$92.80	$92.80
7 purchase totals =	$973.09		$1,051.4309	$1,051.45	$1,051.45	$1,051.50