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	$169.55	3.320%	$175.1791	$175.18	$175.20	$175.20
Purchase #2	$92.49	8.704%	$100.5403	$100.54	$100.55	$100.50
Purchase #3	$213.61	4.301%	$222.7974	$222.80	$222.80	$222.80
Purchase #4	$50.90	9.698%	$55.8363	$55.84	$55.85	$55.80
Purchase #5	$219.76	11.682%	$245.4324	$245.43	$245.45	$245.40
Purchase #6	$32.72	8.160%	$35.39	$35.39	$35.40	$35.40
Purchase #7	$99.31	9.376%	$108.6213	$108.62	$108.60	$108.60
7 purchase totals =	$878.34		$943.7968	$943.80	$943.85	$943.70