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	$240.49	6.407%	$255.8982	$255.90	$255.90	$255.90
Purchase #2	$250.36	7.227%	$268.4535	$268.45	$268.45	$268.50
Purchase #3	$8.78	4.246%	$9.1528	$9.15	$9.15	$9.20
Purchase #4	$59.83	12.219%	$67.1406	$67.14	$67.15	$67.10
Purchase #5	$186.28	9.791%	$204.5187	$204.52	$204.50	$204.50
Purchase #6	$213.90	9.129%	$233.4269	$233.43	$233.45	$233.40
Purchase #7	$42.25	3.517%	$43.7359	$43.74	$43.75	$43.70
7 purchase totals =	$1,001.89		$1,082.3266	$1,082.33	$1,082.35	$1,082.30