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	$79.78	11.805%	$89.198	$89.20	$89.20	$89.20
Purchase #2	$32.33	9.355%	$35.3545	$35.35	$35.35	$35.40
Purchase #3	$212.61	6.115%	$225.6111	$225.61	$225.60	$225.60
Purchase #4	$74.42	5.510%	$78.5205	$78.52	$78.50	$78.50
Purchase #5	$31.38	3.833%	$32.5828	$32.58	$32.60	$32.60
Purchase #6	$207.28	3.400%	$214.3275	$214.33	$214.35	$214.30
Purchase #7	$37.73	7.324%	$40.4933	$40.49	$40.50	$40.50
7 purchase totals =	$675.53		$716.0877	$716.08	$716.10	$716.10