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	$129.83	8.721%	$141.1525	$141.15	$141.15	$141.20
Purchase #2	$131.97	7.638%	$142.0499	$142.05	$142.05	$142.00
Purchase #3	$74.55	12.568%	$83.9194	$83.92	$83.90	$83.90
Purchase #4	$194.25	3.379%	$200.8137	$200.81	$200.80	$200.80
Purchase #5	$19.79	13.364%	$22.4347	$22.43	$22.45	$22.40
Purchase #6	$172.37	4.641%	$180.3697	$180.37	$180.35	$180.40
Purchase #7	$211.54	10.871%	$234.5365	$234.54	$234.55	$234.50
7 purchase totals =	$934.30		$1,005.2764	$1,005.27	$1,005.25	$1,005.20