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	$113.33	10.150%	$124.833	$124.83	$124.85	$124.80
Purchase #2	$220.30	6.336%	$234.2582	$234.26	$234.25	$234.30
Purchase #3	$13.64	6.325%	$14.5027	$14.50	$14.50	$14.50
Purchase #4	$10.83	6.245%	$11.5063	$11.51	$11.50	$11.50
Purchase #5	$180.74	3.601%	$187.2484	$187.25	$187.25	$187.20
Purchase #6	$126.29	3.774%	$131.0562	$131.06	$131.05	$131.10
Purchase #7	$96.80	7.325%	$103.8906	$103.89	$103.90	$103.90
7 purchase totals =	$761.93		$807.2954	$807.30	$807.30	$807.30