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	$22.27	12.406%	$25.0328	$25.03	$25.05	$25.00
Purchase #2	$205.88	7.604%	$221.5351	$221.54	$221.55	$221.50
Purchase #3	$132.38	7.253%	$141.9815	$141.98	$142.00	$142.00
Purchase #4	$121.52	8.130%	$131.3996	$131.40	$131.40	$131.40
Purchase #5	$52.61	3.786%	$54.6018	$54.60	$54.60	$54.60
Purchase #6	$249.85	8.706%	$271.6019	$271.60	$271.60	$271.60
Purchase #7	$225.31	6.807%	$240.6469	$240.65	$240.65	$240.60
7 purchase totals =	$1,009.82		$1,086.7996	$1,086.80	$1,086.85	$1,086.70