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	$118.33	7.741%	$127.4899	$127.49	$127.50	$127.50
Purchase #2	$86.44	6.508%	$92.0655	$92.07	$92.05	$92.10
Purchase #3	$156.72	9.406%	$171.4611	$171.46	$171.45	$171.50
Purchase #4	$244.33	3.497%	$252.8742	$252.87	$252.85	$252.90
Purchase #5	$225.99	7.284%	$242.4511	$242.45	$242.45	$242.50
Purchase #6	$75.94	8.611%	$82.4792	$82.48	$82.50	$82.50
Purchase #7	$217.47	13.295%	$246.3826	$246.38	$246.40	$246.40
7 purchase totals =	$1,125.22		$1,215.2036	$1,215.20	$1,215.20	$1,215.40