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	$168.29	6.273%	$178.8468	$178.85	$178.85	$178.80
Purchase #2	$126.52	12.230%	$141.9934	$141.99	$142.00	$142.00
Purchase #3	$215.54	13.138%	$243.8576	$243.86	$243.85	$243.90
Purchase #4	$133.98	5.653%	$141.5539	$141.55	$141.55	$141.60
Purchase #5	$82.54	9.329%	$90.2402	$90.24	$90.25	$90.20
Purchase #6	$171.94	13.864%	$195.7778	$195.78	$195.80	$195.80
Purchase #7	$108.78	12.743%	$122.6418	$122.64	$122.65	$122.60
7 purchase totals =	$1,007.59		$1,114.9115	$1,114.91	$1,114.95	$1,114.90