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	$208.75	8.182%	$225.8299	$225.83	$225.85	$225.80
Purchase #2	$104.98	9.153%	$114.5888	$114.59	$114.60	$114.60
Purchase #3	$154.41	11.123%	$171.585	$171.59	$171.60	$171.60
Purchase #4	$155.59	4.350%	$162.3582	$162.36	$162.35	$162.40
Purchase #5	$169.92	10.106%	$187.0921	$187.09	$187.10	$187.10
Purchase #6	$201.88	7.314%	$216.6455	$216.65	$216.65	$216.60
Purchase #7	$124.90	5.290%	$131.5072	$131.51	$131.50	$131.50
7 purchase totals =	$1,120.43		$1,209.6067	$1,209.62	$1,209.65	$1,209.60