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	$94.72	10.687%	$104.8427	$104.84	$104.85	$104.80
Purchase #2	$59.51	11.435%	$66.315	$66.32	$66.30	$66.30
Purchase #3	$102.51	3.260%	$105.8518	$105.85	$105.85	$105.90
Purchase #4	$236.68	6.265%	$251.508	$251.51	$251.50	$251.50
Purchase #5	$133.78	7.480%	$143.7867	$143.79	$143.80	$143.80
Purchase #6	$103.71	6.221%	$110.1618	$110.16	$110.15	$110.20
Purchase #7	$223.59	10.710%	$247.5365	$247.54	$247.55	$247.50
7 purchase totals =	$954.50		$1,030.0025	$1,030.01	$1,030.00	$1,030.00