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	$195.26	13.563%	$221.7431	$221.74	$221.75	$221.70
Purchase #2	$102.84	7.631%	$110.6877	$110.69	$110.70	$110.70
Purchase #3	$150.27	12.781%	$169.476	$169.48	$169.50	$169.50
Purchase #4	$210.89	5.554%	$222.6028	$222.60	$222.60	$222.60
Purchase #5	$227.74	11.233%	$253.322	$253.32	$253.30	$253.30
Purchase #6	$227.87	12.709%	$256.83	$256.83	$256.85	$256.80
Purchase #7	$94.60	9.239%	$103.3401	$103.34	$103.35	$103.30
7 purchase totals =	$1,209.47		$1,338.0017	$1,338.00	$1,338.05	$1,337.90