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	$203.32	11.417%	$226.533	$226.53	$226.55	$226.50
Purchase #2	$105.55	10.731%	$116.8766	$116.88	$116.90	$116.90
Purchase #3	$65.49	7.195%	$70.202	$70.20	$70.20	$70.20
Purchase #4	$112.52	4.597%	$117.6925	$117.69	$117.70	$117.70
Purchase #5	$95.47	5.207%	$100.4411	$100.44	$100.45	$100.40
Purchase #6	$39.61	6.615%	$42.2302	$42.23	$42.25	$42.20
Purchase #7	$213.86	7.290%	$229.4504	$229.45	$229.45	$229.50
7 purchase totals =	$835.82		$903.4258	$903.42	$903.50	$903.40