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	$103.52	6.587%	$110.3389	$110.34	$110.35	$110.30
Purchase #2	$247.93	5.803%	$262.3174	$262.32	$262.30	$262.30
Purchase #3	$60.54	7.377%	$65.006	$65.01	$65.00	$65.00
Purchase #4	$74.82	5.347%	$78.8206	$78.82	$78.80	$78.80
Purchase #5	$32.65	12.617%	$36.7695	$36.77	$36.75	$36.80
Purchase #6	$31.25	12.300%	$35.0938	$35.09	$35.10	$35.10
Purchase #7	$213.27	4.361%	$222.5707	$222.57	$222.55	$222.60
7 purchase totals =	$763.98		$810.9169	$810.92	$810.85	$810.90