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	$62.66	5.696%	$66.2291	$66.23	$66.25	$66.20
Purchase #2	$105.42	10.446%	$116.4322	$116.43	$116.45	$116.40
Purchase #3	$203.79	3.243%	$210.3989	$210.40	$210.40	$210.40
Purchase #4	$12.31	10.731%	$13.631	$13.63	$13.65	$13.60
Purchase #5	$11.55	3.360%	$11.9381	$11.94	$11.95	$11.90
Purchase #6	$35.34	6.380%	$37.5947	$37.59	$37.60	$37.60
Purchase #7	$172.87	3.179%	$178.3655	$178.37	$178.35	$178.40
7 purchase totals =	$603.94		$634.5895	$634.59	$634.65	$634.50