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	$84.89	12.311%	$95.3408	$95.34	$95.35	$95.30
Purchase #2	$176.54	13.790%	$200.8849	$200.88	$200.90	$200.90
Purchase #3	$228.81	4.201%	$238.4223	$238.42	$238.40	$238.40
Purchase #4	$222.94	7.671%	$240.0417	$240.04	$240.05	$240.00
Purchase #5	$159.50	5.110%	$167.6505	$167.65	$167.65	$167.70
Purchase #6	$141.32	6.868%	$151.0259	$151.03	$151.05	$151.00
Purchase #7	$119.71	6.552%	$127.5534	$127.55	$127.55	$127.60
7 purchase totals =	$1,133.71		$1,220.9195	$1,220.91	$1,220.95	$1,220.90