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	$151.25	10.663%	$167.3778	$167.38	$167.40	$167.40
Purchase #2	$18.61	9.184%	$20.3191	$20.32	$20.30	$20.30
Purchase #3	$129.78	7.219%	$139.1488	$139.15	$139.15	$139.10
Purchase #4	$176.83	11.206%	$196.6456	$196.65	$196.65	$196.60
Purchase #5	$233.53	13.668%	$265.4489	$265.45	$265.45	$265.40
Purchase #6	$114.46	12.702%	$128.9987	$129.00	$129.00	$129.00
Purchase #7	$176.30	8.195%	$190.7478	$190.75	$190.75	$190.70
7 purchase totals =	$1,000.76		$1,108.6867	$1,108.70	$1,108.70	$1,108.50