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	$102.90	9.497%	$112.6724	$112.67	$112.65	$112.70
Purchase #2	$85.88	11.629%	$95.867	$95.87	$95.85	$95.90
Purchase #3	$35.82	3.558%	$37.0945	$37.09	$37.10	$37.10
Purchase #4	$196.35	5.589%	$207.324	$207.32	$207.30	$207.30
Purchase #5	$87.41	3.451%	$90.4265	$90.43	$90.45	$90.40
Purchase #6	$88.33	11.564%	$98.5445	$98.54	$98.55	$98.50
Purchase #7	$156.62	10.872%	$173.6477	$173.65	$173.65	$173.60
7 purchase totals =	$753.31		$815.5766	$815.57	$815.55	$815.50