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	$27.80	13.126%	$31.449	$31.45	$31.45	$31.40
Purchase #2	$77.53	6.477%	$82.5516	$82.55	$82.55	$82.60
Purchase #3	$235.58	4.160%	$245.3801	$245.38	$245.40	$245.40
Purchase #4	$111.74	12.358%	$125.5488	$125.55	$125.55	$125.50
Purchase #5	$142.88	10.654%	$158.1024	$158.10	$158.10	$158.10
Purchase #6	$213.53	4.407%	$222.9403	$222.94	$222.95	$222.90
Purchase #7	$187.25	10.523%	$206.9543	$206.95	$206.95	$207.00
7 purchase totals =	$996.31		$1,072.9265	$1,072.92	$1,072.95	$1,072.90