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	$125.80	12.275%	$141.242	$141.24	$141.25	$141.20
Purchase #2	$72.89	6.477%	$77.6111	$77.61	$77.60	$77.60
Purchase #3	$35.62	10.755%	$39.4509	$39.45	$39.45	$39.50
Purchase #4	$143.44	5.835%	$151.8097	$151.81	$151.80	$151.80
Purchase #5	$233.74	9.317%	$255.5176	$255.52	$255.50	$255.50
Purchase #6	$76.33	6.155%	$81.0281	$81.03	$81.05	$81.00
Purchase #7	$53.25	13.107%	$60.2295	$60.23	$60.25	$60.20
7 purchase totals =	$741.07		$806.8889	$806.89	$806.90	$806.80