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	$113.90	10.595%	$125.9677	$125.97	$125.95	$126.00
Purchase #2	$172.79	6.665%	$184.3065	$184.31	$184.30	$184.30
Purchase #3	$135.46	11.745%	$151.3698	$151.37	$151.35	$151.40
Purchase #4	$17.91	12.208%	$20.0965	$20.10	$20.10	$20.10
Purchase #5	$73.47	6.566%	$78.294	$78.29	$78.30	$78.30
Purchase #6	$103.37	5.301%	$108.8496	$108.85	$108.85	$108.80
Purchase #7	$137.71	3.327%	$142.2916	$142.29	$142.30	$142.30
7 purchase totals =	$754.61		$811.1757	$811.18	$811.15	$811.20