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	$39.61	13.455%	$44.9395	$44.94	$44.95	$44.90
Purchase #2	$65.61	8.802%	$71.385	$71.39	$71.40	$71.40
Purchase #3	$54.83	7.786%	$59.0991	$59.10	$59.10	$59.10
Purchase #4	$241.59	11.589%	$269.5879	$269.59	$269.60	$269.60
Purchase #5	$209.99	5.561%	$221.6675	$221.67	$221.65	$221.70
Purchase #6	$91.64	5.863%	$97.0129	$97.01	$97.00	$97.00
Purchase #7	$41.52	4.174%	$43.253	$43.25	$43.25	$43.30
7 purchase totals =	$744.79		$806.9449	$806.95	$806.95	$807.00