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	$67.31	6.373%	$71.5997	$71.60	$71.60	$71.60
Purchase #2	$103.78	7.807%	$111.8821	$111.88	$111.90	$111.90
Purchase #3	$179.55	9.402%	$196.4313	$196.43	$196.45	$196.40
Purchase #4	$199.29	7.281%	$213.8003	$213.80	$213.80	$213.80
Purchase #5	$38.90	10.491%	$42.981	$42.98	$43.00	$43.00
Purchase #6	$175.35	11.339%	$195.2329	$195.23	$195.25	$195.20
Purchase #7	$179.95	8.380%	$195.0298	$195.03	$195.05	$195.00
7 purchase totals =	$944.13		$1,026.9571	$1,026.95	$1,027.05	$1,026.90