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	$109.33	7.417%	$117.439	$117.44	$117.45	$117.40
Purchase #2	$239.25	13.536%	$271.6349	$271.63	$271.65	$271.60
Purchase #3	$187.34	4.779%	$196.293	$196.29	$196.30	$196.30
Purchase #4	$51.79	7.179%	$55.508	$55.51	$55.50	$55.50
Purchase #5	$33.51	4.229%	$34.9271	$34.93	$34.95	$34.90
Purchase #6	$159.46	3.268%	$164.6712	$164.67	$164.65	$164.70
Purchase #7	$13.79	11.481%	$15.3732	$15.37	$15.35	$15.40
7 purchase totals =	$794.47		$855.8464	$855.84	$855.85	$855.80