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	$145.26	6.315%	$154.4332	$154.43	$154.45	$154.40
Purchase #2	$67.85	3.657%	$70.3313	$70.33	$70.35	$70.30
Purchase #3	$143.60	3.381%	$148.4551	$148.46	$148.45	$148.50
Purchase #4	$91.77	4.442%	$95.8464	$95.85	$95.85	$95.80
Purchase #5	$101.34	4.516%	$105.9165	$105.92	$105.90	$105.90
Purchase #6	$199.32	4.432%	$208.1539	$208.15	$208.15	$208.20
Purchase #7	$22.30	8.771%	$24.2559	$24.26	$24.25	$24.30
7 purchase totals =	$771.44		$807.3923	$807.40	$807.40	$807.40