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	$208.52	6.667%	$222.422	$222.42	$222.40	$222.40
Purchase #2	$245.61	8.134%	$265.5879	$265.59	$265.60	$265.60
Purchase #3	$172.77	12.120%	$193.7097	$193.71	$193.70	$193.70
Purchase #4	$127.30	12.780%	$143.5689	$143.57	$143.55	$143.60
Purchase #5	$7.89	10.193%	$8.6942	$8.69	$8.70	$8.70
Purchase #6	$179.46	11.701%	$200.4586	$200.46	$200.45	$200.50
Purchase #7	$81.75	10.844%	$90.615	$90.62	$90.60	$90.60
7 purchase totals =	$1,023.30		$1,125.0563	$1,125.06	$1,125.00	$1,125.10