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	$161.90	11.636%	$180.7387	$180.74	$180.75	$180.70
Purchase #2	$67.29	13.382%	$76.2947	$76.29	$76.30	$76.30
Purchase #3	$165.55	8.862%	$180.221	$180.22	$180.20	$180.20
Purchase #4	$210.42	11.576%	$234.7782	$234.78	$234.80	$234.80
Purchase #5	$211.88	4.238%	$220.8595	$220.86	$220.85	$220.90
Purchase #6	$42.31	6.849%	$45.2078	$45.21	$45.20	$45.20
Purchase #7	$111.51	10.505%	$123.2241	$123.22	$123.20	$123.20
7 purchase totals =	$970.86		$1,061.3240	$1,061.32	$1,061.30	$1,061.30