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	$50.59	4.113%	$52.6708	$52.67	$52.65	$52.70
Purchase #2	$249.29	6.497%	$265.4864	$265.49	$265.50	$265.50
Purchase #3	$32.88	12.667%	$37.0449	$37.04	$37.05	$37.00
Purchase #4	$151.31	8.584%	$164.2985	$164.30	$164.30	$164.30
Purchase #5	$139.47	9.382%	$152.5551	$152.56	$152.55	$152.60
Purchase #6	$78.52	11.747%	$87.7437	$87.74	$87.75	$87.70
Purchase #7	$20.29	7.301%	$21.7714	$21.77	$21.75	$21.80
7 purchase totals =	$722.35		$781.5708	$781.57	$781.55	$781.60