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	$98.50	11.203%	$109.535	$109.54	$109.55	$109.50
Purchase #2	$123.40	6.690%	$131.6555	$131.66	$131.65	$131.70
Purchase #3	$63.31	12.181%	$71.0218	$71.02	$71.00	$71.00
Purchase #4	$111.73	4.656%	$116.9321	$116.93	$116.95	$116.90
Purchase #5	$34.83	6.325%	$37.033	$37.03	$37.05	$37.00
Purchase #6	$87.62	6.199%	$93.0516	$93.05	$93.05	$93.10
Purchase #7	$10.97	3.557%	$11.3602	$11.36	$11.35	$11.40
7 purchase totals =	$530.36		$570.5892	$570.59	$570.60	$570.60