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	$237.76	12.575%	$267.6583	$267.66	$267.65	$267.70
Purchase #2	$231.70	6.644%	$247.0941	$247.09	$247.10	$247.10
Purchase #3	$66.52	9.565%	$72.8826	$72.88	$72.90	$72.90
Purchase #4	$90.41	4.767%	$94.7198	$94.72	$94.70	$94.70
Purchase #5	$52.54	12.288%	$58.9961	$59.00	$59.00	$59.00
Purchase #6	$23.49	4.119%	$24.4576	$24.46	$24.45	$24.50
Purchase #7	$242.67	11.585%	$270.7833	$270.78	$270.80	$270.80
7 purchase totals =	$945.09		$1,036.5918	$1,036.59	$1,036.60	$1,036.70