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	$55.26	7.759%	$59.5476	$59.55	$59.55	$59.50
Purchase #2	$228.86	3.441%	$236.7351	$236.74	$236.75	$236.70
Purchase #3	$20.37	3.531%	$21.0893	$21.09	$21.10	$21.10
Purchase #4	$146.82	3.120%	$151.4008	$151.40	$151.40	$151.40
Purchase #5	$145.79	11.222%	$162.1506	$162.15	$162.15	$162.20
Purchase #6	$239.78	9.423%	$262.3745	$262.37	$262.35	$262.40
Purchase #7	$245.72	7.729%	$264.7117	$264.71	$264.70	$264.70
7 purchase totals =	$1,082.60		$1,158.0096	$1,158.01	$1,158.00	$1,158.00