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	$191.81	11.330%	$213.5421	$213.54	$213.55	$213.50
Purchase #2	$63.45	11.713%	$70.8819	$70.88	$70.90	$70.90
Purchase #3	$206.80	6.330%	$219.8904	$219.89	$219.90	$219.90
Purchase #4	$143.66	4.699%	$150.4106	$150.41	$150.40	$150.40
Purchase #5	$9.73	13.684%	$11.0615	$11.06	$11.05	$11.10
Purchase #6	$51.56	6.755%	$55.0429	$55.04	$55.05	$55.00
Purchase #7	$46.81	10.514%	$51.7316	$51.73	$51.75	$51.70
7 purchase totals =	$713.82		$772.5610	$772.55	$772.60	$772.50