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	$38.40	8.216%	$41.5549	$41.55	$41.55	$41.60
Purchase #2	$213.88	12.611%	$240.8524	$240.85	$240.85	$240.90
Purchase #3	$41.55	4.816%	$43.551	$43.55	$43.55	$43.60
Purchase #4	$238.27	10.513%	$263.3193	$263.32	$263.30	$263.30
Purchase #5	$211.50	7.435%	$227.225	$227.23	$227.25	$227.20
Purchase #6	$176.72	13.177%	$200.0064	$200.01	$200.00	$200.00
Purchase #7	$138.77	7.195%	$148.7545	$148.75	$148.75	$148.80
7 purchase totals =	$1,059.09		$1,165.2635	$1,165.26	$1,165.25	$1,165.40