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	$133.72	9.487%	$146.406	$146.41	$146.40	$146.40
Purchase #2	$213.54	4.277%	$222.6731	$222.67	$222.65	$222.70
Purchase #3	$116.25	10.230%	$128.1424	$128.14	$128.15	$128.10
Purchase #4	$168.50	4.328%	$175.7927	$175.79	$175.80	$175.80
Purchase #5	$64.71	4.520%	$67.6349	$67.63	$67.65	$67.60
Purchase #6	$68.55	8.342%	$74.2684	$74.27	$74.25	$74.30
Purchase #7	$176.45	7.541%	$189.7561	$189.76	$189.75	$189.80
7 purchase totals =	$941.72		$1,004.6736	$1,004.67	$1,004.65	$1,004.70