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	$217.41	4.784%	$227.8109	$227.81	$227.80	$227.80
Purchase #2	$188.78	4.179%	$196.6691	$196.67	$196.65	$196.70
Purchase #3	$104.26	5.569%	$110.0662	$110.07	$110.05	$110.10
Purchase #4	$47.48	9.286%	$51.889	$51.89	$51.90	$51.90
Purchase #5	$80.73	11.277%	$89.8339	$89.83	$89.85	$89.80
Purchase #6	$178.71	8.629%	$194.1309	$194.13	$194.15	$194.10
Purchase #7	$33.93	12.790%	$38.2696	$38.27	$38.25	$38.30
7 purchase totals =	$851.30		$908.6696	$908.67	$908.65	$908.70