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	$101.39	5.345%	$106.8093	$106.81	$106.80	$106.80
Purchase #2	$59.81	12.839%	$67.489	$67.49	$67.50	$67.50
Purchase #3	$104.90	13.806%	$119.3825	$119.38	$119.40	$119.40
Purchase #4	$195.64	8.476%	$212.2224	$212.22	$212.20	$212.20
Purchase #5	$176.56	3.416%	$182.5913	$182.59	$182.60	$182.60
Purchase #6	$229.93	12.341%	$258.3057	$258.31	$258.30	$258.30
Purchase #7	$140.97	8.235%	$152.5789	$152.58	$152.60	$152.60
7 purchase totals =	$1,009.20		$1,099.3791	$1,099.38	$1,099.40	$1,099.40