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	$165.97	11.626%	$185.2657	$185.27	$185.25	$185.30
Purchase #2	$187.48	4.308%	$195.5566	$195.56	$195.55	$195.60
Purchase #3	$74.67	9.730%	$81.9354	$81.94	$81.95	$81.90
Purchase #4	$113.94	8.739%	$123.8972	$123.90	$123.90	$123.90
Purchase #5	$31.82	12.143%	$35.6839	$35.68	$35.70	$35.70
Purchase #6	$7.88	9.807%	$8.6528	$8.65	$8.65	$8.70
Purchase #7	$85.61	5.197%	$90.0592	$90.06	$90.05	$90.10
7 purchase totals =	$667.37		$721.0508	$721.06	$721.05	$721.20