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	$114.82	11.720%	$128.2769	$128.28	$128.30	$128.30
Purchase #2	$222.83	11.204%	$247.7959	$247.80	$247.80	$247.80
Purchase #3	$178.53	9.488%	$195.4689	$195.47	$195.45	$195.50
Purchase #4	$221.38	13.214%	$250.6332	$250.63	$250.65	$250.60
Purchase #5	$93.64	12.626%	$105.463	$105.46	$105.45	$105.50
Purchase #6	$93.54	7.856%	$100.8885	$100.89	$100.90	$100.90
Purchase #7	$113.66	4.829%	$119.1486	$119.15	$119.15	$119.10
7 purchase totals =	$1,038.40		$1,147.6750	$1,147.68	$1,147.70	$1,147.70