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	$242.60	3.274%	$250.5427	$250.54	$250.55	$250.50
Purchase #2	$162.28	4.254%	$169.1834	$169.18	$169.20	$169.20
Purchase #3	$41.49	10.591%	$45.8842	$45.88	$45.90	$45.90
Purchase #4	$233.66	11.258%	$259.9654	$259.97	$259.95	$260.00
Purchase #5	$242.32	8.153%	$262.0763	$262.08	$262.10	$262.10
Purchase #6	$31.77	6.829%	$33.9396	$33.94	$33.95	$33.90
Purchase #7	$113.79	13.812%	$129.5067	$129.51	$129.50	$129.50
7 purchase totals =	$1,067.91		$1,151.0983	$1,151.10	$1,151.15	$1,151.10