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	$52.66	13.800%	$59.9271	$59.93	$59.95	$59.90
Purchase #2	$233.96	7.189%	$250.7794	$250.78	$250.80	$250.80
Purchase #3	$90.91	4.856%	$95.3246	$95.32	$95.30	$95.30
Purchase #4	$114.64	12.429%	$128.8886	$128.89	$128.90	$128.90
Purchase #5	$231.57	13.356%	$262.4985	$262.50	$262.50	$262.50
Purchase #6	$181.69	5.149%	$191.0452	$191.05	$191.05	$191.00
Purchase #7	$74.53	7.288%	$79.9617	$79.96	$79.95	$80.00
7 purchase totals =	$979.96		$1,068.4251	$1,068.43	$1,068.45	$1,068.40