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	$134.65	7.577%	$144.8524	$144.85	$144.85	$144.90
Purchase #2	$89.38	9.544%	$97.9104	$97.91	$97.90	$97.90
Purchase #3	$179.93	10.570%	$198.9486	$198.95	$198.95	$198.90
Purchase #4	$108.88	3.137%	$112.2956	$112.30	$112.30	$112.30
Purchase #5	$229.72	11.848%	$256.9372	$256.94	$256.95	$256.90
Purchase #6	$143.78	3.482%	$148.7864	$148.79	$148.80	$148.80
Purchase #7	$122.42	8.705%	$133.0767	$133.08	$133.10	$133.10
7 purchase totals =	$1,008.76		$1,092.8073	$1,092.82	$1,092.85	$1,092.80