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	$31.63	13.389%	$35.8649	$35.86	$35.85	$35.90
Purchase #2	$74.44	11.171%	$82.7557	$82.76	$82.75	$82.80
Purchase #3	$208.32	12.637%	$234.6454	$234.65	$234.65	$234.60
Purchase #4	$99.38	12.756%	$112.0569	$112.06	$112.05	$112.10
Purchase #5	$53.41	11.105%	$59.3412	$59.34	$59.35	$59.30
Purchase #6	$56.67	7.468%	$60.9021	$60.90	$60.90	$60.90
Purchase #7	$94.37	7.548%	$101.493	$101.49	$101.50	$101.50
7 purchase totals =	$618.22		$687.0592	$687.06	$687.05	$687.10