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	$55.76	12.726%	$62.856	$62.86	$62.85	$62.90
Purchase #2	$151.77	10.835%	$168.2143	$168.21	$168.20	$168.20
Purchase #3	$54.26	4.833%	$56.8824	$56.88	$56.90	$56.90
Purchase #4	$9.26	12.837%	$10.4487	$10.45	$10.45	$10.40
Purchase #5	$10.77	10.529%	$11.904	$11.90	$11.90	$11.90
Purchase #6	$94.64	8.729%	$102.9011	$102.90	$102.90	$102.90
Purchase #7	$75.73	3.709%	$78.5388	$78.54	$78.55	$78.50
7 purchase totals =	$452.19		$491.7453	$491.74	$491.75	$491.70