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	$218.46	8.792%	$237.667	$237.67	$237.65	$237.70
Purchase #2	$223.90	9.270%	$244.6555	$244.66	$244.65	$244.70
Purchase #3	$65.54	10.843%	$72.6465	$72.65	$72.65	$72.60
Purchase #4	$6.76	7.387%	$7.2594	$7.26	$7.25	$7.30
Purchase #5	$224.88	4.714%	$235.4808	$235.48	$235.50	$235.50
Purchase #6	$130.44	5.400%	$137.4838	$137.48	$137.50	$137.50
Purchase #7	$131.39	6.463%	$139.8817	$139.88	$139.90	$139.90
7 purchase totals =	$1,001.37		$1,075.0747	$1,075.08	$1,075.10	$1,075.20