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	$161.54	12.553%	$181.8181	$181.82	$181.80	$181.80
Purchase #2	$137.39	4.744%	$143.9078	$143.91	$143.90	$143.90
Purchase #3	$41.81	8.247%	$45.2581	$45.26	$45.25	$45.30
Purchase #4	$185.33	13.503%	$210.3551	$210.36	$210.35	$210.40
Purchase #5	$78.59	7.525%	$84.5039	$84.50	$84.50	$84.50
Purchase #6	$89.93	11.635%	$100.3934	$100.39	$100.40	$100.40
Purchase #7	$153.52	3.248%	$158.5063	$158.51	$158.50	$158.50
7 purchase totals =	$848.11		$924.7427	$924.75	$924.70	$924.80