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	$90.37	5.819%	$95.6286	$95.63	$95.65	$95.60
Purchase #2	$33.70	3.376%	$34.8377	$34.84	$34.85	$34.80
Purchase #3	$217.41	4.774%	$227.7892	$227.79	$227.80	$227.80
Purchase #4	$12.50	6.532%	$13.3165	$13.32	$13.30	$13.30
Purchase #5	$86.74	4.198%	$90.3813	$90.38	$90.40	$90.40
Purchase #6	$237.44	12.603%	$267.3646	$267.36	$267.35	$267.40
Purchase #7	$127.30	12.261%	$142.9083	$142.91	$142.90	$142.90
7 purchase totals =	$805.46		$872.2262	$872.23	$872.25	$872.20