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	$21.35	13.584%	$24.2502	$24.25	$24.25	$24.30
Purchase #2	$89.61	5.455%	$94.4982	$94.50	$94.50	$94.50
Purchase #3	$178.74	3.382%	$184.785	$184.79	$184.80	$184.80
Purchase #4	$194.36	9.316%	$212.4666	$212.47	$212.45	$212.50
Purchase #5	$164.80	9.475%	$180.4148	$180.41	$180.40	$180.40
Purchase #6	$46.77	13.463%	$53.0666	$53.07	$53.05	$53.10
Purchase #7	$32.88	13.871%	$37.4408	$37.44	$37.45	$37.40
7 purchase totals =	$728.51		$786.9222	$786.93	$786.90	$787.00