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	$213.76	11.458%	$238.2526	$238.25	$238.25	$238.30
Purchase #2	$60.93	6.700%	$65.0123	$65.01	$65.00	$65.00
Purchase #3	$63.86	9.815%	$70.1279	$70.13	$70.15	$70.10
Purchase #4	$134.67	10.598%	$148.9423	$148.94	$148.95	$148.90
Purchase #5	$56.53	12.256%	$63.4583	$63.46	$63.45	$63.50
Purchase #6	$148.47	5.231%	$156.2365	$156.24	$156.25	$156.20
Purchase #7	$81.76	6.280%	$86.8945	$86.89	$86.90	$86.90
7 purchase totals =	$759.98		$828.9244	$828.92	$828.95	$828.90