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	$234.29	12.467%	$263.4989	$263.50	$263.50	$263.50
Purchase #2	$40.38	4.520%	$42.2052	$42.21	$42.20	$42.20
Purchase #3	$165.52	13.713%	$188.2178	$188.22	$188.20	$188.20
Purchase #4	$94.65	6.176%	$100.4956	$100.50	$100.50	$100.50
Purchase #5	$196.86	11.868%	$220.2233	$220.22	$220.20	$220.20
Purchase #6	$135.80	11.328%	$151.1834	$151.18	$151.20	$151.20
Purchase #7	$205.63	11.765%	$229.8224	$229.82	$229.80	$229.80
7 purchase totals =	$1,073.13		$1,195.6466	$1,195.65	$1,195.60	$1,195.60