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	$162.50	7.542%	$174.7558	$174.76	$174.75	$174.80
Purchase #2	$37.59	9.741%	$41.2516	$41.25	$41.25	$41.30
Purchase #3	$184.60	13.691%	$209.8736	$209.87	$209.85	$209.90
Purchase #4	$46.67	11.102%	$51.8513	$51.85	$51.85	$51.90
Purchase #5	$249.45	6.726%	$266.228	$266.23	$266.25	$266.20
Purchase #6	$158.46	10.495%	$175.0904	$175.09	$175.10	$175.10
Purchase #7	$85.91	5.306%	$90.4684	$90.47	$90.45	$90.50
7 purchase totals =	$925.18		$1,009.5191	$1,009.52	$1,009.50	$1,009.70