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	$127.60	7.402%	$137.045	$137.05	$137.05	$137.00
Purchase #2	$245.47	3.305%	$253.5828	$253.58	$253.60	$253.60
Purchase #3	$247.91	13.256%	$280.7729	$280.77	$280.75	$280.80
Purchase #4	$148.38	3.244%	$153.1934	$153.19	$153.20	$153.20
Purchase #5	$67.77	7.514%	$72.8622	$72.86	$72.85	$72.90
Purchase #6	$139.74	8.503%	$151.6221	$151.62	$151.60	$151.60
Purchase #7	$244.85	11.470%	$272.9343	$272.93	$272.95	$272.90
7 purchase totals =	$1,221.72		$1,322.0127	$1,322.00	$1,322.00	$1,322.00