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	$43.59	8.382%	$47.2437	$47.24	$47.25	$47.20
Purchase #2	$161.43	4.216%	$168.2359	$168.24	$168.25	$168.20
Purchase #3	$175.80	5.156%	$184.8642	$184.86	$184.85	$184.90
Purchase #4	$151.56	3.214%	$156.4311	$156.43	$156.45	$156.40
Purchase #5	$201.98	4.269%	$210.6025	$210.60	$210.60	$210.60
Purchase #6	$129.75	9.834%	$142.5096	$142.51	$142.50	$142.50
Purchase #7	$215.58	12.301%	$242.0985	$242.10	$242.10	$242.10
7 purchase totals =	$1,079.69		$1,151.9855	$1,151.98	$1,152.00	$1,151.90