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	$55.50	7.115%	$59.4488	$59.45	$59.45	$59.40
Purchase #2	$25.57	7.578%	$27.5077	$27.51	$27.50	$27.50
Purchase #3	$168.37	8.641%	$182.9189	$182.92	$182.90	$182.90
Purchase #4	$160.27	5.642%	$169.3124	$169.31	$169.30	$169.30
Purchase #5	$104.29	13.536%	$118.4067	$118.41	$118.40	$118.40
Purchase #6	$232.75	10.854%	$258.0127	$258.01	$258.00	$258.00
Purchase #7	$193.27	11.439%	$215.3782	$215.38	$215.40	$215.40
7 purchase totals =	$940.02		$1,030.9854	$1,030.99	$1,030.95	$1,030.90