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	$54.58	9.663%	$59.8541	$59.85	$59.85	$59.90
Purchase #2	$104.43	11.375%	$116.3089	$116.31	$116.30	$116.30
Purchase #3	$168.59	3.266%	$174.0961	$174.10	$174.10	$174.10
Purchase #4	$119.57	12.462%	$134.4708	$134.47	$134.45	$134.50
Purchase #5	$32.76	7.109%	$35.0889	$35.09	$35.10	$35.10
Purchase #6	$174.38	4.625%	$182.4451	$182.45	$182.45	$182.40
Purchase #7	$214.30	8.142%	$231.7483	$231.75	$231.75	$231.70
7 purchase totals =	$868.61		$934.0122	$934.02	$934.00	$934.00