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	$221.44	10.114%	$243.8364	$243.84	$243.85	$243.80
Purchase #2	$164.25	5.622%	$173.4841	$173.48	$173.50	$173.50
Purchase #3	$76.61	11.675%	$85.5542	$85.55	$85.55	$85.60
Purchase #4	$123.55	7.622%	$132.967	$132.97	$132.95	$133.00
Purchase #5	$45.63	4.499%	$47.6829	$47.68	$47.70	$47.70
Purchase #6	$81.96	8.800%	$89.1725	$89.17	$89.15	$89.20
Purchase #7	$85.88	11.531%	$95.7828	$95.78	$95.80	$95.80
7 purchase totals =	$799.32		$868.4799	$868.47	$868.50	$868.60