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	$126.35	3.297%	$130.5158	$130.52	$130.50	$130.50
Purchase #2	$106.37	4.649%	$111.3151	$111.32	$111.30	$111.30
Purchase #3	$136.72	3.517%	$141.5284	$141.53	$141.55	$141.50
Purchase #4	$67.54	5.855%	$71.4945	$71.49	$71.50	$71.50
Purchase #5	$226.89	11.303%	$252.5354	$252.54	$252.55	$252.50
Purchase #6	$150.57	9.645%	$165.0925	$165.09	$165.10	$165.10
Purchase #7	$181.73	12.798%	$204.9878	$204.99	$205.00	$205.00
7 purchase totals =	$996.17		$1,077.4695	$1,077.48	$1,077.50	$1,077.40