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	$65.36	9.482%	$71.5574	$71.56	$71.55	$71.60
Purchase #2	$55.42	3.732%	$57.4883	$57.49	$57.50	$57.50
Purchase #3	$192.90	10.868%	$213.8644	$213.86	$213.85	$213.90
Purchase #4	$185.64	12.491%	$208.8283	$208.83	$208.85	$208.80
Purchase #5	$240.36	8.751%	$261.3939	$261.39	$261.40	$261.40
Purchase #6	$144.65	7.524%	$155.5335	$155.53	$155.55	$155.50
Purchase #7	$176.47	4.268%	$184.0017	$184.00	$184.00	$184.00
7 purchase totals =	$1,060.80		$1,152.6675	$1,152.66	$1,152.70	$1,152.70