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	$220.98	6.709%	$235.8055	$235.81	$235.80	$235.80
Purchase #2	$221.95	7.312%	$238.179	$238.18	$238.20	$238.20
Purchase #3	$159.73	7.637%	$171.9286	$171.93	$171.95	$171.90
Purchase #4	$81.71	9.376%	$89.3711	$89.37	$89.35	$89.40
Purchase #5	$29.58	5.296%	$31.1466	$31.15	$31.15	$31.10
Purchase #6	$13.91	7.102%	$14.8979	$14.90	$14.90	$14.90
Purchase #7	$212.90	11.684%	$237.7752	$237.78	$237.80	$237.80
7 purchase totals =	$940.76		$1,019.1039	$1,019.12	$1,019.15	$1,019.10