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	$226.26	8.815%	$246.2048	$246.20	$246.20	$246.20
Purchase #2	$65.43	3.149%	$67.4904	$67.49	$67.50	$67.50
Purchase #3	$86.96	12.471%	$97.8048	$97.80	$97.80	$97.80
Purchase #4	$101.37	3.609%	$105.0284	$105.03	$105.05	$105.00
Purchase #5	$179.59	9.549%	$196.739	$196.74	$196.75	$196.70
Purchase #6	$40.85	6.359%	$43.4477	$43.45	$43.45	$43.40
Purchase #7	$154.57	6.592%	$164.7593	$164.76	$164.75	$164.80
7 purchase totals =	$855.03		$921.4744	$921.47	$921.50	$921.40