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	$31.60	13.334%	$35.8135	$35.81	$35.80	$35.80
Purchase #2	$42.34	5.193%	$44.5387	$44.54	$44.55	$44.50
Purchase #3	$72.72	7.291%	$78.022	$78.02	$78.00	$78.00
Purchase #4	$105.97	6.410%	$112.7627	$112.76	$112.75	$112.80
Purchase #5	$94.52	6.823%	$100.9691	$100.97	$100.95	$101.00
Purchase #6	$80.76	13.117%	$91.3533	$91.35	$91.35	$91.40
Purchase #7	$198.98	8.493%	$215.8794	$215.88	$215.90	$215.90
7 purchase totals =	$626.89		$679.3387	$679.33	$679.30	$679.40