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	$57.47	3.165%	$59.2889	$59.29	$59.30	$59.30
Purchase #2	$46.76	3.858%	$48.564	$48.56	$48.55	$48.60
Purchase #3	$180.57	4.725%	$189.1019	$189.10	$189.10	$189.10
Purchase #4	$230.45	9.208%	$251.6698	$251.67	$251.65	$251.70
Purchase #5	$80.39	5.146%	$84.5269	$84.53	$84.55	$84.50
Purchase #6	$35.95	12.757%	$40.5361	$40.54	$40.55	$40.50
Purchase #7	$89.52	3.359%	$92.527	$92.53	$92.55	$92.50
7 purchase totals =	$721.11		$766.2146	$766.22	$766.25	$766.20