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	$129.57	10.554%	$143.2448	$143.24	$143.25	$143.20
Purchase #2	$204.47	12.223%	$229.4624	$229.46	$229.45	$229.50
Purchase #3	$43.95	10.490%	$48.5604	$48.56	$48.55	$48.60
Purchase #4	$206.94	11.758%	$231.272	$231.27	$231.25	$231.30
Purchase #5	$146.33	10.124%	$161.1444	$161.14	$161.15	$161.10
Purchase #6	$227.56	6.542%	$242.447	$242.45	$242.45	$242.40
Purchase #7	$25.96	13.808%	$29.5446	$29.54	$29.55	$29.50
7 purchase totals =	$984.78		$1,085.6756	$1,085.66	$1,085.65	$1,085.60