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	$71.95	9.725%	$78.9471	$78.95	$78.95	$78.90
Purchase #2	$248.89	8.221%	$269.3512	$269.35	$269.35	$269.40
Purchase #3	$213.90	6.795%	$228.4345	$228.43	$228.45	$228.40
Purchase #4	$217.52	10.257%	$239.831	$239.83	$239.85	$239.80
Purchase #5	$184.40	3.870%	$191.5363	$191.54	$191.55	$191.50
Purchase #6	$153.95	3.861%	$159.894	$159.89	$159.90	$159.90
Purchase #7	$108.79	13.477%	$123.4516	$123.45	$123.45	$123.50
7 purchase totals =	$1,199.40		$1,291.4457	$1,291.44	$1,291.50	$1,291.40