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	$183.86	8.469%	$199.4311	$199.43	$199.45	$199.40
Purchase #2	$129.74	12.151%	$145.5047	$145.50	$145.50	$145.50
Purchase #3	$153.32	7.303%	$164.517	$164.52	$164.50	$164.50
Purchase #4	$41.72	12.462%	$46.9191	$46.92	$46.90	$46.90
Purchase #5	$146.64	3.202%	$151.3354	$151.34	$151.35	$151.30
Purchase #6	$130.29	6.851%	$139.2162	$139.22	$139.20	$139.20
Purchase #7	$168.61	9.750%	$185.0495	$185.05	$185.05	$185.00
7 purchase totals =	$954.18		$1,031.9730	$1,031.98	$1,031.95	$1,031.80