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	$163.85	5.200%	$172.3702	$172.37	$172.35	$172.40
Purchase #2	$31.36	11.824%	$35.068	$35.07	$35.05	$35.10
Purchase #3	$156.49	7.522%	$168.2612	$168.26	$168.25	$168.30
Purchase #4	$190.70	13.545%	$216.5303	$216.53	$216.55	$216.50
Purchase #5	$19.25	7.858%	$20.7627	$20.76	$20.75	$20.80
Purchase #6	$54.45	9.417%	$59.5776	$59.58	$59.60	$59.60
Purchase #7	$89.39	6.691%	$95.3711	$95.37	$95.35	$95.40
7 purchase totals =	$705.49		$767.9411	$767.94	$767.90	$768.10