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	$96.78	7.114%	$103.6649	$103.66	$103.65	$103.70
Purchase #2	$55.86	6.493%	$59.487	$59.49	$59.50	$59.50
Purchase #3	$46.59	12.572%	$52.4473	$52.45	$52.45	$52.40
Purchase #4	$54.83	4.442%	$57.2655	$57.27	$57.25	$57.30
Purchase #5	$204.83	3.849%	$212.7139	$212.71	$212.70	$212.70
Purchase #6	$168.87	10.319%	$186.2957	$186.30	$186.30	$186.30
Purchase #7	$138.84	6.141%	$147.3662	$147.37	$147.35	$147.40
7 purchase totals =	$766.60		$819.2405	$819.25	$819.20	$819.30