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	$154.59	9.815%	$169.763	$169.76	$169.75	$169.80
Purchase #2	$92.93	7.123%	$99.5494	$99.55	$99.55	$99.50
Purchase #3	$77.51	10.599%	$85.7253	$85.73	$85.75	$85.70
Purchase #4	$52.34	4.557%	$54.7251	$54.73	$54.75	$54.70
Purchase #5	$158.62	10.697%	$175.5876	$175.59	$175.60	$175.60
Purchase #6	$83.38	13.482%	$94.6213	$94.62	$94.60	$94.60
Purchase #7	$182.62	4.864%	$191.5026	$191.50	$191.50	$191.50
7 purchase totals =	$801.99		$871.4743	$871.48	$871.50	$871.40