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	$73.52	6.744%	$78.4782	$78.48	$78.50	$78.50
Purchase #2	$16.31	3.559%	$16.8905	$16.89	$16.90	$16.90
Purchase #3	$38.43	4.842%	$40.2908	$40.29	$40.30	$40.30
Purchase #4	$225.29	10.158%	$248.175	$248.18	$248.20	$248.20
Purchase #5	$205.34	12.659%	$231.334	$231.33	$231.35	$231.30
Purchase #6	$58.60	6.456%	$62.3832	$62.38	$62.40	$62.40
Purchase #7	$178.57	9.371%	$195.3038	$195.30	$195.30	$195.30
7 purchase totals =	$796.06		$872.8555	$872.85	$872.95	$872.90