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	$191.65	12.566%	$215.7327	$215.73	$215.75	$215.70
Purchase #2	$169.45	3.162%	$174.808	$174.81	$174.80	$174.80
Purchase #3	$132.27	8.621%	$143.673	$143.67	$143.65	$143.70
Purchase #4	$125.41	11.549%	$139.8936	$139.89	$139.90	$139.90
Purchase #5	$167.68	12.566%	$188.7507	$188.75	$188.75	$188.80
Purchase #6	$92.64	13.826%	$105.4484	$105.45	$105.45	$105.40
Purchase #7	$79.95	4.518%	$83.5621	$83.56	$83.55	$83.60
7 purchase totals =	$959.05		$1,051.8685	$1,051.86	$1,051.85	$1,051.90