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	$67.43	3.492%	$69.7847	$69.78	$69.80	$69.80
Purchase #2	$45.49	13.616%	$51.6839	$51.68	$51.70	$51.70
Purchase #3	$95.81	3.842%	$99.491	$99.49	$99.50	$99.50
Purchase #4	$108.80	3.602%	$112.719	$112.72	$112.70	$112.70
Purchase #5	$32.63	8.144%	$35.2874	$35.29	$35.30	$35.30
Purchase #6	$141.86	13.119%	$160.4706	$160.47	$160.45	$160.50
Purchase #7	$64.42	7.567%	$69.2947	$69.29	$69.30	$69.30
7 purchase totals =	$556.44		$598.7313	$598.72	$598.75	$598.80