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	$109.57	3.809%	$113.7435	$113.74	$113.75	$113.70
Purchase #2	$199.96	8.660%	$217.2765	$217.28	$217.30	$217.30
Purchase #3	$88.75	6.399%	$94.4291	$94.43	$94.45	$94.40
Purchase #4	$250.31	12.515%	$281.6363	$281.64	$281.65	$281.60
Purchase #5	$186.64	6.533%	$198.8332	$198.83	$198.85	$198.80
Purchase #6	$143.38	7.762%	$154.5092	$154.51	$154.50	$154.50
Purchase #7	$64.85	3.119%	$66.8727	$66.87	$66.85	$66.90
7 purchase totals =	$1,043.46		$1,127.3005	$1,127.30	$1,127.35	$1,127.20