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	$115.78	4.677%	$121.195	$121.20	$121.20	$121.20
Purchase #2	$40.67	4.434%	$42.4733	$42.47	$42.45	$42.50
Purchase #3	$12.46	7.584%	$13.405	$13.41	$13.40	$13.40
Purchase #4	$175.63	11.631%	$196.0575	$196.06	$196.05	$196.10
Purchase #5	$248.63	6.334%	$264.3782	$264.38	$264.40	$264.40
Purchase #6	$233.89	7.194%	$250.716	$250.72	$250.70	$250.70
Purchase #7	$234.96	7.683%	$253.012	$253.01	$253.00	$253.00
7 purchase totals =	$1,062.02		$1,141.2370	$1,141.25	$1,141.20	$1,141.30