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	$127.65	4.114%	$132.9015	$132.90	$132.90	$132.90
Purchase #2	$51.74	7.313%	$55.5237	$55.52	$55.50	$55.50
Purchase #3	$156.28	6.189%	$165.9522	$165.95	$165.95	$166.00
Purchase #4	$174.46	6.456%	$185.7231	$185.72	$185.70	$185.70
Purchase #5	$247.32	4.108%	$257.4799	$257.48	$257.50	$257.50
Purchase #6	$76.39	11.800%	$85.404	$85.40	$85.40	$85.40
Purchase #7	$200.78	12.813%	$226.5059	$226.51	$226.50	$226.50
7 purchase totals =	$1,034.62		$1,109.4903	$1,109.48	$1,109.45	$1,109.50