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	$131.44	6.849%	$140.4423	$140.44	$140.45	$140.40
Purchase #2	$235.82	7.640%	$253.8366	$253.84	$253.85	$253.80
Purchase #3	$164.61	5.437%	$173.5598	$173.56	$173.55	$173.60
Purchase #4	$134.81	5.328%	$141.9927	$141.99	$142.00	$142.00
Purchase #5	$174.55	12.226%	$195.8905	$195.89	$195.90	$195.90
Purchase #6	$57.52	7.861%	$62.0416	$62.04	$62.05	$62.00
Purchase #7	$212.86	7.479%	$228.7798	$228.78	$228.80	$228.80
7 purchase totals =	$1,111.61		$1,196.5433	$1,196.54	$1,196.60	$1,196.50