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	$10.48	5.554%	$11.0621	$11.06	$11.05	$11.10
Purchase #2	$19.33	8.195%	$20.9141	$20.91	$20.90	$20.90
Purchase #3	$88.98	11.829%	$99.5054	$99.51	$99.50	$99.50
Purchase #4	$176.57	9.434%	$193.2276	$193.23	$193.25	$193.20
Purchase #5	$32.61	3.517%	$33.7569	$33.76	$33.75	$33.80
Purchase #6	$27.71	13.604%	$31.4797	$31.48	$31.50	$31.50
Purchase #7	$67.44	3.745%	$69.9656	$69.97	$69.95	$70.00
7 purchase totals =	$423.12		$459.9114	$459.92	$459.90	$460.00