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	$33.93	5.365%	$35.7503	$35.75	$35.75	$35.80
Purchase #2	$172.36	3.597%	$178.5598	$178.56	$178.55	$178.60
Purchase #3	$202.98	6.734%	$216.6487	$216.65	$216.65	$216.60
Purchase #4	$213.27	4.271%	$222.3788	$222.38	$222.40	$222.40
Purchase #5	$244.31	9.117%	$266.5837	$266.58	$266.60	$266.60
Purchase #6	$152.53	12.445%	$171.5124	$171.51	$171.50	$171.50
Purchase #7	$60.57	7.330%	$65.0098	$65.01	$65.00	$65.00
7 purchase totals =	$1,079.95		$1,156.4435	$1,156.44	$1,156.45	$1,156.50