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	$72.54	8.164%	$78.4622	$78.46	$78.45	$78.50
Purchase #2	$173.25	13.534%	$196.6977	$196.70	$196.70	$196.70
Purchase #3	$9.85	11.821%	$11.0144	$11.01	$11.00	$11.00
Purchase #4	$152.64	9.540%	$167.2019	$167.20	$167.20	$167.20
Purchase #5	$198.70	5.410%	$209.4497	$209.45	$209.45	$209.40
Purchase #6	$229.63	10.642%	$254.0672	$254.07	$254.05	$254.10
Purchase #7	$174.51	3.187%	$180.0716	$180.07	$180.05	$180.10
7 purchase totals =	$1,011.12		$1,096.9647	$1,096.96	$1,096.90	$1,097.00