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	$247.31	3.498%	$255.9609	$255.96	$255.95	$256.00
Purchase #2	$71.87	9.570%	$78.748	$78.75	$78.75	$78.70
Purchase #3	$222.34	11.231%	$247.311	$247.31	$247.30	$247.30
Purchase #4	$137.71	3.483%	$142.5064	$142.51	$142.50	$142.50
Purchase #5	$42.64	10.268%	$47.0183	$47.02	$47.00	$47.00
Purchase #6	$217.28	9.738%	$238.4387	$238.44	$238.45	$238.40
Purchase #7	$164.66	4.354%	$171.8293	$171.83	$171.85	$171.80
7 purchase totals =	$1,103.81		$1,181.8126	$1,181.82	$1,181.80	$1,181.70