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	$199.41	6.383%	$212.1383	$212.14	$212.15	$212.10
Purchase #2	$17.69	9.538%	$19.3773	$19.38	$19.40	$19.40
Purchase #3	$25.83	13.611%	$29.3457	$29.35	$29.35	$29.30
Purchase #4	$234.39	11.728%	$261.8793	$261.88	$261.90	$261.90
Purchase #5	$64.38	4.853%	$67.5044	$67.50	$67.50	$67.50
Purchase #6	$159.49	5.832%	$168.7915	$168.79	$168.80	$168.80
Purchase #7	$222.31	8.509%	$241.2264	$241.23	$241.25	$241.20
7 purchase totals =	$923.50		$1,000.2629	$1,000.27	$1,000.35	$1,000.20