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	$48.89	7.174%	$52.3974	$52.40	$52.40	$52.40
Purchase #2	$102.44	10.316%	$113.0077	$113.01	$113.00	$113.00
Purchase #3	$52.34	4.183%	$54.5294	$54.53	$54.55	$54.50
Purchase #4	$163.49	12.711%	$184.2712	$184.27	$184.25	$184.30
Purchase #5	$33.49	13.755%	$38.0965	$38.10	$38.10	$38.10
Purchase #6	$59.37	6.354%	$63.1424	$63.14	$63.15	$63.10
Purchase #7	$127.57	3.222%	$131.6803	$131.68	$131.70	$131.70
7 purchase totals =	$587.59		$637.1249	$637.13	$637.15	$637.10