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	$139.34	9.624%	$152.7501	$152.75	$152.75	$152.80
Purchase #2	$180.46	10.142%	$198.7623	$198.76	$198.75	$198.80
Purchase #3	$120.68	4.225%	$125.7787	$125.78	$125.80	$125.80
Purchase #4	$41.71	3.132%	$43.0164	$43.02	$43.00	$43.00
Purchase #5	$188.92	11.431%	$210.5154	$210.52	$210.50	$210.50
Purchase #6	$250.72	3.791%	$260.2248	$260.22	$260.20	$260.20
Purchase #7	$42.64	6.159%	$45.2662	$45.27	$45.25	$45.30
7 purchase totals =	$964.47		$1,036.3139	$1,036.32	$1,036.25	$1,036.40