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	$222.40	7.691%	$239.5048	$239.50	$239.50	$239.50
Purchase #2	$183.34	9.584%	$200.9113	$200.91	$200.90	$200.90
Purchase #3	$51.37	6.514%	$54.7162	$54.72	$54.70	$54.70
Purchase #4	$198.59	12.552%	$223.517	$223.52	$223.50	$223.50
Purchase #5	$235.73	11.276%	$262.3109	$262.31	$262.30	$262.30
Purchase #6	$91.60	8.768%	$99.6315	$99.63	$99.65	$99.60
Purchase #7	$95.48	9.797%	$104.8342	$104.83	$104.85	$104.80
7 purchase totals =	$1,078.51		$1,185.4259	$1,185.42	$1,185.40	$1,185.30