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	$210.92	11.840%	$235.8929	$235.89	$235.90	$235.90
Purchase #2	$133.35	13.548%	$151.4163	$151.42	$151.40	$151.40
Purchase #3	$27.42	13.705%	$31.1779	$31.18	$31.20	$31.20
Purchase #4	$35.31	11.371%	$39.3251	$39.33	$39.35	$39.30
Purchase #5	$131.54	11.665%	$146.8841	$146.88	$146.90	$146.90
Purchase #6	$47.78	3.725%	$49.5598	$49.56	$49.55	$49.60
Purchase #7	$99.55	8.132%	$107.6454	$107.65	$107.65	$107.60
7 purchase totals =	$685.87		$761.9015	$761.91	$761.95	$761.90