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	$99.27	10.276%	$109.471	$109.47	$109.45	$109.50
Purchase #2	$192.30	12.186%	$215.7337	$215.73	$215.75	$215.70
Purchase #3	$184.49	7.448%	$198.2308	$198.23	$198.25	$198.20
Purchase #4	$58.81	4.493%	$61.4523	$61.45	$61.45	$61.50
Purchase #5	$20.90	12.813%	$23.5779	$23.58	$23.60	$23.60
Purchase #6	$222.86	5.644%	$235.4382	$235.44	$235.45	$235.40
Purchase #7	$89.93	10.731%	$99.5804	$99.58	$99.60	$99.60
7 purchase totals =	$868.56		$943.4843	$943.48	$943.55	$943.50