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	$99.36	6.146%	$105.4667	$105.47	$105.45	$105.50
Purchase #2	$220.36	11.783%	$246.325	$246.33	$246.35	$246.30
Purchase #3	$81.69	8.468%	$88.6075	$88.61	$88.60	$88.60
Purchase #4	$115.27	3.644%	$119.4704	$119.47	$119.45	$119.50
Purchase #5	$169.25	10.120%	$186.3781	$186.38	$186.40	$186.40
Purchase #6	$197.96	3.461%	$204.8114	$204.81	$204.80	$204.80
Purchase #7	$45.45	12.534%	$51.1467	$51.15	$51.15	$51.10
7 purchase totals =	$929.34		$1,002.2058	$1,002.22	$1,002.20	$1,002.20