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	$78.86	10.813%	$87.3871	$87.39	$87.40	$87.40
Purchase #2	$169.49	5.252%	$178.3916	$178.39	$178.40	$178.40
Purchase #3	$236.47	7.358%	$253.8695	$253.87	$253.85	$253.90
Purchase #4	$177.77	10.782%	$196.9372	$196.94	$196.95	$196.90
Purchase #5	$126.47	11.412%	$140.9028	$140.90	$140.90	$140.90
Purchase #6	$222.35	3.184%	$229.4296	$229.43	$229.45	$229.40
Purchase #7	$95.32	5.156%	$100.2347	$100.23	$100.25	$100.20
7 purchase totals =	$1,106.73		$1,187.1525	$1,187.15	$1,187.20	$1,187.10