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	$34.69	3.598%	$35.9381	$35.94	$35.95	$35.90
Purchase #2	$178.79	6.669%	$190.7135	$190.71	$190.70	$190.70
Purchase #3	$64.72	3.139%	$66.7516	$66.75	$66.75	$66.80
Purchase #4	$179.83	5.502%	$189.7242	$189.72	$189.70	$189.70
Purchase #5	$175.42	12.542%	$197.4212	$197.42	$197.40	$197.40
Purchase #6	$163.37	7.565%	$175.7289	$175.73	$175.75	$175.70
Purchase #7	$86.77	3.218%	$89.5623	$89.56	$89.55	$89.60
7 purchase totals =	$883.59		$945.8398	$945.83	$945.80	$945.80