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	$118.79	12.243%	$133.3335	$133.33	$133.35	$133.30
Purchase #2	$102.42	8.486%	$111.1114	$111.11	$111.10	$111.10
Purchase #3	$18.75	3.293%	$19.3674	$19.37	$19.35	$19.40
Purchase #4	$16.88	12.296%	$18.9556	$18.96	$18.95	$19.00
Purchase #5	$56.67	4.534%	$59.2394	$59.24	$59.25	$59.20
Purchase #6	$182.45	4.325%	$190.341	$190.34	$190.35	$190.30
Purchase #7	$186.52	11.569%	$208.0985	$208.10	$208.10	$208.10
7 purchase totals =	$682.48		$740.4468	$740.45	$740.45	$740.40