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	$69.44	4.266%	$72.4023	$72.40	$72.40	$72.40
Purchase #2	$233.50	6.166%	$247.8976	$247.90	$247.90	$247.90
Purchase #3	$189.89	5.808%	$200.9188	$200.92	$200.90	$200.90
Purchase #4	$198.31	10.631%	$219.3923	$219.39	$219.40	$219.40
Purchase #5	$18.83	13.828%	$21.4338	$21.43	$21.45	$21.40
Purchase #6	$151.69	7.631%	$163.2655	$163.27	$163.25	$163.30
Purchase #7	$222.27	7.534%	$239.0158	$239.02	$239.00	$239.00
7 purchase totals =	$1,083.93		$1,164.3261	$1,164.33	$1,164.30	$1,164.30