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	$208.59	7.494%	$224.2217	$224.22	$224.20	$224.20
Purchase #2	$154.63	11.828%	$172.9196	$172.92	$172.90	$172.90
Purchase #3	$6.37	4.370%	$6.6484	$6.65	$6.65	$6.60
Purchase #4	$197.51	8.291%	$213.8856	$213.89	$213.90	$213.90
Purchase #5	$61.51	6.773%	$65.6761	$65.68	$65.70	$65.70
Purchase #6	$79.40	13.164%	$89.8522	$89.85	$89.85	$89.90
Purchase #7	$213.68	3.529%	$221.2208	$221.22	$221.20	$221.20
7 purchase totals =	$921.69		$994.4244	$994.43	$994.40	$994.40