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	$201.84	10.735%	$223.5075	$223.51	$223.50	$223.50
Purchase #2	$222.39	4.769%	$232.9958	$233.00	$233.00	$233.00
Purchase #3	$113.82	8.151%	$123.0975	$123.10	$123.10	$123.10
Purchase #4	$90.94	4.357%	$94.9023	$94.90	$94.90	$94.90
Purchase #5	$244.42	11.122%	$271.6044	$271.60	$271.60	$271.60
Purchase #6	$35.31	8.297%	$38.2397	$38.24	$38.25	$38.20
Purchase #7	$21.39	5.699%	$22.609	$22.61	$22.60	$22.60
7 purchase totals =	$930.11		$1,006.9562	$1,006.96	$1,006.95	$1,006.90