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	$113.72	11.449%	$126.7398	$126.74	$126.75	$126.70
Purchase #2	$81.28	11.368%	$90.5199	$90.52	$90.50	$90.50
Purchase #3	$43.57	13.176%	$49.3108	$49.31	$49.30	$49.30
Purchase #4	$215.91	3.214%	$222.8493	$222.85	$222.85	$222.80
Purchase #5	$140.36	3.374%	$145.0957	$145.10	$145.10	$145.10
Purchase #6	$129.44	8.149%	$139.9881	$139.99	$140.00	$140.00
Purchase #7	$190.47	3.215%	$196.5936	$196.59	$196.60	$196.60
7 purchase totals =	$914.75		$971.0972	$971.10	$971.10	$971.00