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	$118.80	12.812%	$134.0207	$134.02	$134.00	$134.00
Purchase #2	$102.89	8.384%	$111.5163	$111.52	$111.50	$111.50
Purchase #3	$78.75	8.671%	$85.5784	$85.58	$85.60	$85.60
Purchase #4	$59.49	11.736%	$66.4717	$66.47	$66.45	$66.50
Purchase #5	$191.67	3.656%	$198.6775	$198.68	$198.70	$198.70
Purchase #6	$162.60	3.655%	$168.543	$168.54	$168.55	$168.50
Purchase #7	$6.25	6.796%	$6.6748	$6.67	$6.65	$6.70
7 purchase totals =	$720.45		$771.4824	$771.48	$771.45	$771.50