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	$238.46	4.423%	$249.0071	$249.01	$249.00	$249.00
Purchase #2	$155.53	5.147%	$163.5351	$163.54	$163.55	$163.50
Purchase #3	$186.88	13.640%	$212.3704	$212.37	$212.35	$212.40
Purchase #4	$144.84	4.294%	$151.0594	$151.06	$151.05	$151.10
Purchase #5	$31.49	11.232%	$35.027	$35.03	$35.05	$35.00
Purchase #6	$118.44	7.641%	$127.49	$127.49	$127.50	$127.50
Purchase #7	$71.97	8.769%	$78.281	$78.28	$78.30	$78.30
7 purchase totals =	$947.61		$1,016.7700	$1,016.78	$1,016.80	$1,016.80