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	$35.50	8.408%	$38.4848	$38.48	$38.50	$38.50
Purchase #2	$20.78	12.233%	$23.322	$23.32	$23.30	$23.30
Purchase #3	$165.77	11.715%	$185.19	$185.19	$185.20	$185.20
Purchase #4	$203.69	6.226%	$216.3717	$216.37	$216.35	$216.40
Purchase #5	$244.51	5.703%	$258.4544	$258.45	$258.45	$258.50
Purchase #6	$51.79	9.690%	$56.8085	$56.81	$56.80	$56.80
Purchase #7	$201.94	10.548%	$223.2406	$223.24	$223.25	$223.20
7 purchase totals =	$923.98		$1,001.8720	$1,001.86	$1,001.85	$1,001.90