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	$229.29	7.387%	$246.2277	$246.23	$246.25	$246.20
Purchase #2	$119.72	3.330%	$123.7067	$123.71	$123.70	$123.70
Purchase #3	$60.33	3.522%	$62.4548	$62.45	$62.45	$62.50
Purchase #4	$176.36	12.773%	$198.8865	$198.89	$198.90	$198.90
Purchase #5	$85.87	10.194%	$94.6236	$94.62	$94.60	$94.60
Purchase #6	$218.94	12.598%	$246.5221	$246.52	$246.50	$246.50
Purchase #7	$160.32	3.370%	$165.7228	$165.72	$165.70	$165.70
7 purchase totals =	$1,050.83		$1,138.1442	$1,138.14	$1,138.10	$1,138.10