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	$54.56	9.132%	$59.5424	$59.54	$59.55	$59.50
Purchase #2	$75.93	9.826%	$83.3909	$83.39	$83.40	$83.40
Purchase #3	$98.53	4.622%	$103.0841	$103.08	$103.10	$103.10
Purchase #4	$118.75	3.679%	$123.1188	$123.12	$123.10	$123.10
Purchase #5	$139.46	6.566%	$148.6169	$148.62	$148.60	$148.60
Purchase #6	$223.79	12.343%	$251.4124	$251.41	$251.40	$251.40
Purchase #7	$204.26	11.258%	$227.2556	$227.26	$227.25	$227.30
7 purchase totals =	$915.28		$996.4211	$996.42	$996.40	$996.40