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	$119.25	6.562%	$127.0752	$127.08	$127.10	$127.10
Purchase #2	$208.97	6.387%	$222.3169	$222.32	$222.30	$222.30
Purchase #3	$228.77	11.503%	$255.0854	$255.09	$255.10	$255.10
Purchase #4	$45.46	3.198%	$46.9138	$46.91	$46.90	$46.90
Purchase #5	$37.55	12.310%	$42.1724	$42.17	$42.15	$42.20
Purchase #6	$88.84	5.690%	$93.895	$93.90	$93.90	$93.90
Purchase #7	$26.57	11.697%	$29.6779	$29.68	$29.70	$29.70
7 purchase totals =	$755.41		$817.1366	$817.15	$817.15	$817.20