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	$127.31	3.426%	$131.6716	$131.67	$131.65	$131.70
Purchase #2	$144.77	6.339%	$153.947	$153.95	$153.95	$153.90
Purchase #3	$229.71	3.725%	$238.2667	$238.27	$238.25	$238.30
Purchase #4	$79.73	9.726%	$87.4845	$87.48	$87.50	$87.50
Purchase #5	$237.52	11.142%	$263.9845	$263.98	$264.00	$264.00
Purchase #6	$83.78	3.461%	$86.6796	$86.68	$86.70	$86.70
Purchase #7	$98.64	10.696%	$109.1905	$109.19	$109.20	$109.20
7 purchase totals =	$1,001.46		$1,071.2244	$1,071.22	$1,071.25	$1,071.30