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	$73.30	7.454%	$78.7638	$78.76	$78.75	$78.80
Purchase #2	$218.83	4.126%	$227.8589	$227.86	$227.85	$227.90
Purchase #3	$123.48	3.342%	$127.6067	$127.61	$127.60	$127.60
Purchase #4	$198.25	8.660%	$215.4185	$215.42	$215.40	$215.40
Purchase #5	$209.87	11.728%	$234.4836	$234.48	$234.50	$234.50
Purchase #6	$16.64	3.788%	$17.2703	$17.27	$17.25	$17.30
Purchase #7	$139.68	9.486%	$152.93	$152.93	$152.95	$152.90
7 purchase totals =	$980.05		$1,054.3318	$1,054.33	$1,054.30	$1,054.40