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	$190.45	9.566%	$208.6684	$208.67	$208.65	$208.70
Purchase #2	$230.46	5.168%	$242.3702	$242.37	$242.35	$242.40
Purchase #3	$24.67	10.846%	$27.3457	$27.35	$27.35	$27.30
Purchase #4	$5.72	7.350%	$6.1404	$6.14	$6.15	$6.10
Purchase #5	$100.69	8.735%	$109.4853	$109.49	$109.50	$109.50
Purchase #6	$124.89	12.333%	$140.2927	$140.29	$140.30	$140.30
Purchase #7	$90.66	9.469%	$99.2446	$99.24	$99.25	$99.20
7 purchase totals =	$767.54		$833.5473	$833.55	$833.55	$833.50