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	$190.44	5.284%	$200.5028	$200.50	$200.50	$200.50
Purchase #2	$248.98	8.619%	$270.4396	$270.44	$270.45	$270.40
Purchase #3	$43.95	3.838%	$45.6368	$45.64	$45.65	$45.60
Purchase #4	$23.46	6.652%	$25.0206	$25.02	$25.00	$25.00
Purchase #5	$159.79	12.261%	$179.3819	$179.38	$179.40	$179.40
Purchase #6	$80.73	13.824%	$91.8901	$91.89	$91.90	$91.90
Purchase #7	$238.46	10.228%	$262.8497	$262.85	$262.85	$262.80
7 purchase totals =	$985.81		$1,075.7215	$1,075.72	$1,075.75	$1,075.60