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	$238.87	11.201%	$265.6258	$265.63	$265.65	$265.60
Purchase #2	$59.88	12.617%	$67.4351	$67.44	$67.45	$67.40
Purchase #3	$107.54	10.257%	$118.5704	$118.57	$118.55	$118.60
Purchase #4	$151.51	11.260%	$168.57	$168.57	$168.55	$168.60
Purchase #5	$173.79	6.760%	$185.5382	$185.54	$185.55	$185.50
Purchase #6	$59.72	7.190%	$64.0139	$64.01	$64.00	$64.00
Purchase #7	$196.71	10.357%	$217.0833	$217.08	$217.10	$217.10
7 purchase totals =	$988.02		$1,086.8367	$1,086.84	$1,086.85	$1,086.80