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	$226.67	6.572%	$241.5668	$241.57	$241.55	$241.60
Purchase #2	$193.44	3.682%	$200.5625	$200.56	$200.55	$200.60
Purchase #3	$141.98	7.469%	$152.5845	$152.58	$152.60	$152.60
Purchase #4	$112.39	6.182%	$119.3379	$119.34	$119.35	$119.30
Purchase #5	$113.72	13.856%	$129.477	$129.48	$129.50	$129.50
Purchase #6	$135.47	12.387%	$152.2507	$152.25	$152.25	$152.30
Purchase #7	$190.75	9.834%	$209.5084	$209.51	$209.50	$209.50
7 purchase totals =	$1,114.42		$1,205.2878	$1,205.29	$1,205.30	$1,205.40