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	$205.47	3.340%	$212.3327	$212.33	$212.35	$212.30
Purchase #2	$38.93	9.183%	$42.5049	$42.50	$42.50	$42.50
Purchase #3	$27.73	6.548%	$29.5458	$29.55	$29.55	$29.50
Purchase #4	$57.93	12.773%	$65.3294	$65.33	$65.35	$65.30
Purchase #5	$55.29	10.850%	$61.289	$61.29	$61.30	$61.30
Purchase #6	$111.68	7.255%	$119.7824	$119.78	$119.80	$119.80
Purchase #7	$244.71	13.241%	$277.1121	$277.11	$277.10	$277.10
7 purchase totals =	$741.74		$807.8963	$807.89	$807.95	$807.80