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	$89.87	5.132%	$94.4821	$94.48	$94.50	$94.50
Purchase #2	$182.33	4.291%	$190.1538	$190.15	$190.15	$190.20
Purchase #3	$212.31	4.309%	$221.4584	$221.46	$221.45	$221.50
Purchase #4	$92.66	12.525%	$104.2657	$104.27	$104.25	$104.30
Purchase #5	$226.84	11.770%	$253.5391	$253.54	$253.55	$253.50
Purchase #6	$206.78	4.554%	$216.1968	$216.20	$216.20	$216.20
Purchase #7	$16.81	10.341%	$18.5483	$18.55	$18.55	$18.50
7 purchase totals =	$1,027.60		$1,098.6442	$1,098.65	$1,098.65	$1,098.70