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	$43.36	7.266%	$46.5105	$46.51	$46.50	$46.50
Purchase #2	$44.80	12.461%	$50.3825	$50.38	$50.40	$50.40
Purchase #3	$240.47	9.353%	$262.9612	$262.96	$262.95	$263.00
Purchase #4	$91.85	11.614%	$102.5175	$102.52	$102.50	$102.50
Purchase #5	$154.84	8.218%	$167.5648	$167.56	$167.55	$167.60
Purchase #6	$134.65	13.797%	$153.2277	$153.23	$153.25	$153.20
Purchase #7	$231.30	9.443%	$253.1417	$253.14	$253.15	$253.10
7 purchase totals =	$941.27		$1,036.3059	$1,036.30	$1,036.30	$1,036.30