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	$96.61	11.665%	$107.8796	$107.88	$107.90	$107.90
Purchase #2	$94.57	8.784%	$102.877	$102.88	$102.90	$102.90
Purchase #3	$59.93	4.120%	$62.3991	$62.40	$62.40	$62.40
Purchase #4	$195.86	4.804%	$205.2691	$205.27	$205.25	$205.30
Purchase #5	$59.66	5.497%	$62.9395	$62.94	$62.95	$62.90
Purchase #6	$65.74	9.165%	$71.7651	$71.77	$71.75	$71.80
Purchase #7	$80.79	5.776%	$85.4564	$85.46	$85.45	$85.50
7 purchase totals =	$653.16		$698.5858	$698.60	$698.60	$698.70