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	$20.60	11.278%	$22.9233	$22.92	$22.90	$22.90
Purchase #2	$22.51	5.642%	$23.78	$23.78	$23.80	$23.80
Purchase #3	$227.91	12.566%	$256.5492	$256.55	$256.55	$256.50
Purchase #4	$81.49	6.857%	$87.0778	$87.08	$87.10	$87.10
Purchase #5	$65.82	8.341%	$71.31	$71.31	$71.30	$71.30
Purchase #6	$105.74	3.533%	$109.4758	$109.48	$109.50	$109.50
Purchase #7	$136.64	10.543%	$151.046	$151.05	$151.05	$151.00
7 purchase totals =	$660.71		$722.1621	$722.17	$722.20	$722.10