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	$165.89	8.235%	$179.551	$179.55	$179.55	$179.60
Purchase #2	$180.33	9.145%	$196.8212	$196.82	$196.80	$196.80
Purchase #3	$198.39	7.264%	$212.801	$212.80	$212.80	$212.80
Purchase #4	$243.92	12.826%	$275.2052	$275.21	$275.20	$275.20
Purchase #5	$121.98	5.512%	$128.7035	$128.70	$128.70	$128.70
Purchase #6	$158.27	4.215%	$164.9411	$164.94	$164.95	$164.90
Purchase #7	$102.82	10.578%	$113.6963	$113.70	$113.70	$113.70
7 purchase totals =	$1,171.60		$1,271.7193	$1,271.72	$1,271.70	$1,271.70