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	$69.72	11.222%	$77.544	$77.54	$77.55	$77.50
Purchase #2	$223.50	6.850%	$238.8098	$238.81	$238.80	$238.80
Purchase #3	$148.62	7.799%	$160.2109	$160.21	$160.20	$160.20
Purchase #4	$137.71	4.737%	$144.2333	$144.23	$144.25	$144.20
Purchase #5	$59.93	11.504%	$66.8243	$66.82	$66.80	$66.80
Purchase #6	$70.61	11.255%	$78.5572	$78.56	$78.55	$78.60
Purchase #7	$201.53	13.745%	$229.2303	$229.23	$229.25	$229.20
7 purchase totals =	$911.62		$995.4098	$995.40	$995.40	$995.30