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	$61.63	9.871%	$67.7135	$67.71	$67.70	$67.70
Purchase #2	$247.56	4.321%	$258.2571	$258.26	$258.25	$258.30
Purchase #3	$88.83	6.218%	$94.3534	$94.35	$94.35	$94.40
Purchase #4	$163.68	5.772%	$173.1276	$173.13	$173.15	$173.10
Purchase #5	$40.89	7.362%	$43.9003	$43.90	$43.90	$43.90
Purchase #6	$140.57	4.843%	$147.3778	$147.38	$147.40	$147.40
Purchase #7	$113.71	13.201%	$128.7209	$128.72	$128.70	$128.70
7 purchase totals =	$856.87		$913.4506	$913.45	$913.45	$913.50