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	$113.72	7.694%	$122.4696	$122.47	$122.45	$122.50
Purchase #2	$19.66	6.274%	$20.8935	$20.89	$20.90	$20.90
Purchase #3	$135.29	4.799%	$141.7826	$141.78	$141.80	$141.80
Purchase #4	$167.80	9.284%	$183.3786	$183.38	$183.40	$183.40
Purchase #5	$144.75	12.452%	$162.7743	$162.77	$162.75	$162.80
Purchase #6	$246.25	13.391%	$279.2253	$279.23	$279.25	$279.20
Purchase #7	$164.54	6.820%	$175.7616	$175.76	$175.75	$175.80
7 purchase totals =	$992.01		$1,086.2855	$1,086.28	$1,086.30	$1,086.40