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	$6.66	5.259%	$7.0102	$7.01	$7.00	$7.00
Purchase #2	$205.58	10.650%	$227.4743	$227.47	$227.45	$227.50
Purchase #3	$158.80	10.409%	$175.3295	$175.33	$175.35	$175.30
Purchase #4	$178.50	12.344%	$200.534	$200.53	$200.55	$200.50
Purchase #5	$239.74	10.712%	$265.4209	$265.42	$265.40	$265.40
Purchase #6	$42.31	6.383%	$45.0106	$45.01	$45.00	$45.00
Purchase #7	$184.70	4.392%	$192.812	$192.81	$192.80	$192.80
7 purchase totals =	$1,016.29		$1,113.5915	$1,113.58	$1,113.55	$1,113.50