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	$225.61	10.155%	$248.5207	$248.52	$248.50	$248.50
Purchase #2	$112.85	6.232%	$119.8828	$119.88	$119.90	$119.90
Purchase #3	$178.68	5.284%	$188.1215	$188.12	$188.10	$188.10
Purchase #4	$74.54	8.626%	$80.9698	$80.97	$80.95	$81.00
Purchase #5	$242.51	7.166%	$259.8883	$259.89	$259.90	$259.90
Purchase #6	$112.75	12.717%	$127.0884	$127.09	$127.10	$127.10
Purchase #7	$10.48	12.241%	$11.7629	$11.76	$11.75	$11.80
7 purchase totals =	$957.42		$1,036.2344	$1,036.23	$1,036.20	$1,036.30