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	$73.50	7.173%	$78.7722	$78.77	$78.75	$78.80
Purchase #2	$238.99	13.299%	$270.7733	$270.77	$270.75	$270.80
Purchase #3	$32.99	5.564%	$34.8256	$34.83	$34.85	$34.80
Purchase #4	$58.90	13.489%	$66.845	$66.85	$66.85	$66.80
Purchase #5	$162.57	4.408%	$169.7361	$169.74	$169.75	$169.70
Purchase #6	$211.56	8.395%	$229.3205	$229.32	$229.30	$229.30
Purchase #7	$242.58	5.371%	$255.609	$255.61	$255.60	$255.60
7 purchase totals =	$1,021.09		$1,105.8817	$1,105.89	$1,105.85	$1,105.80