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	$31.95	11.430%	$35.6019	$35.60	$35.60	$35.60
Purchase #2	$91.61	8.609%	$99.4967	$99.50	$99.50	$99.50
Purchase #3	$10.65	7.578%	$11.4571	$11.46	$11.45	$11.50
Purchase #4	$158.94	6.216%	$168.8197	$168.82	$168.80	$168.80
Purchase #5	$136.41	13.274%	$154.5171	$154.52	$154.50	$154.50
Purchase #6	$154.94	8.592%	$168.2524	$168.25	$168.25	$168.30
Purchase #7	$52.94	6.204%	$56.2244	$56.22	$56.20	$56.20
7 purchase totals =	$637.44		$694.3693	$694.37	$694.30	$694.40