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	$80.75	9.648%	$88.5408	$88.54	$88.55	$88.50
Purchase #2	$59.73	3.543%	$61.8462	$61.85	$61.85	$61.80
Purchase #3	$114.85	3.162%	$118.4816	$118.48	$118.50	$118.50
Purchase #4	$69.55	9.537%	$76.183	$76.18	$76.20	$76.20
Purchase #5	$124.66	6.103%	$132.268	$132.27	$132.25	$132.30
Purchase #6	$203.52	9.538%	$222.9317	$222.93	$222.95	$222.90
Purchase #7	$33.56	5.828%	$35.5159	$35.52	$35.50	$35.50
7 purchase totals =	$686.62		$735.7672	$735.77	$735.80	$735.70