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	$129.59	9.203%	$141.5162	$141.52	$141.50	$141.50
Purchase #2	$117.60	8.449%	$127.536	$127.54	$127.55	$127.50
Purchase #3	$100.37	7.118%	$107.5143	$107.51	$107.50	$107.50
Purchase #4	$226.31	6.835%	$241.7783	$241.78	$241.80	$241.80
Purchase #5	$156.83	5.269%	$165.0934	$165.09	$165.10	$165.10
Purchase #6	$225.48	7.627%	$242.6774	$242.68	$242.70	$242.70
Purchase #7	$77.53	6.226%	$82.357	$82.36	$82.35	$82.40
7 purchase totals =	$1,033.71		$1,108.4726	$1,108.48	$1,108.50	$1,108.50