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	$9.64	3.573%	$9.9844	$9.98	$10.00	$10.00
Purchase #2	$131.85	7.529%	$141.777	$141.78	$141.80	$141.80
Purchase #3	$36.71	12.299%	$41.225	$41.23	$41.25	$41.20
Purchase #4	$197.53	3.173%	$203.7976	$203.80	$203.80	$203.80
Purchase #5	$145.78	3.273%	$150.5514	$150.55	$150.55	$150.60
Purchase #6	$54.94	13.756%	$62.4975	$62.50	$62.50	$62.50
Purchase #7	$127.57	3.136%	$131.5706	$131.57	$131.55	$131.60
7 purchase totals =	$704.02		$741.4035	$741.41	$741.45	$741.50