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	$154.69	9.325%	$169.1148	$169.11	$169.10	$169.10
Purchase #2	$74.95	7.784%	$80.7841	$80.78	$80.80	$80.80
Purchase #3	$70.76	13.455%	$80.2808	$80.28	$80.30	$80.30
Purchase #4	$112.35	6.230%	$119.3494	$119.35	$119.35	$119.30
Purchase #5	$56.38	9.837%	$61.9261	$61.93	$61.95	$61.90
Purchase #6	$127.30	11.778%	$142.2934	$142.29	$142.30	$142.30
Purchase #7	$92.59	8.193%	$100.1759	$100.18	$100.20	$100.20
7 purchase totals =	$689.02		$753.9245	$753.92	$754.00	$753.90