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	$154.53	6.650%	$164.8062	$164.81	$164.80	$164.80
Purchase #2	$133.78	6.560%	$142.556	$142.56	$142.55	$142.60
Purchase #3	$171.31	10.385%	$189.1005	$189.10	$189.10	$189.10
Purchase #4	$7.32	3.505%	$7.5766	$7.58	$7.60	$7.60
Purchase #5	$52.72	12.229%	$59.1671	$59.17	$59.15	$59.20
Purchase #6	$84.55	3.368%	$87.3976	$87.40	$87.40	$87.40
Purchase #7	$10.75	9.200%	$11.739	$11.74	$11.75	$11.70
7 purchase totals =	$614.96		$662.3430	$662.36	$662.35	$662.40