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	$191.68	13.764%	$218.0628	$218.06	$218.05	$218.10
Purchase #2	$154.85	9.468%	$169.5112	$169.51	$169.50	$169.50
Purchase #3	$185.47	12.275%	$208.2364	$208.24	$208.25	$208.20
Purchase #4	$82.43	12.589%	$92.8071	$92.81	$92.80	$92.80
Purchase #5	$104.73	3.783%	$108.6919	$108.69	$108.70	$108.70
Purchase #6	$48.60	13.338%	$55.0823	$55.08	$55.10	$55.10
Purchase #7	$228.78	10.796%	$253.4791	$253.48	$253.50	$253.50
7 purchase totals =	$996.54		$1,105.8708	$1,105.87	$1,105.90	$1,105.90