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	$246.57	9.215%	$269.2914	$269.29	$269.30	$269.30
Purchase #2	$60.32	11.492%	$67.252	$67.25	$67.25	$67.30
Purchase #3	$194.31	13.113%	$219.7899	$219.79	$219.80	$219.80
Purchase #4	$194.89	9.770%	$213.9308	$213.93	$213.95	$213.90
Purchase #5	$164.91	10.459%	$182.1579	$182.16	$182.15	$182.20
Purchase #6	$110.32	4.766%	$115.5779	$115.58	$115.60	$115.60
Purchase #7	$36.80	12.508%	$41.4029	$41.40	$41.40	$41.40
7 purchase totals =	$1,008.12		$1,109.4028	$1,109.40	$1,109.45	$1,109.50