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	$223.83	6.306%	$237.9447	$237.94	$237.95	$237.90
Purchase #2	$51.82	4.257%	$54.026	$54.03	$54.05	$54.00
Purchase #3	$160.76	11.672%	$179.5239	$179.52	$179.50	$179.50
Purchase #4	$106.81	9.719%	$117.1909	$117.19	$117.20	$117.20
Purchase #5	$77.42	12.588%	$87.1656	$87.17	$87.15	$87.20
Purchase #6	$98.35	11.731%	$109.8874	$109.89	$109.90	$109.90
Purchase #7	$200.95	10.232%	$221.5112	$221.51	$221.50	$221.50
7 purchase totals =	$919.94		$1,007.2497	$1,007.25	$1,007.25	$1,007.20