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	$200.35	7.742%	$215.8611	$215.86	$215.85	$215.90
Purchase #2	$217.84	12.686%	$245.4752	$245.48	$245.50	$245.50
Purchase #3	$37.62	12.317%	$42.2537	$42.25	$42.25	$42.30
Purchase #4	$7.25	4.201%	$7.5546	$7.55	$7.55	$7.60
Purchase #5	$107.94	7.467%	$115.9999	$116.00	$116.00	$116.00
Purchase #6	$184.99	8.259%	$200.2683	$200.27	$200.25	$200.30
Purchase #7	$171.72	6.149%	$182.2791	$182.28	$182.30	$182.30
7 purchase totals =	$927.71		$1,009.6919	$1,009.69	$1,009.70	$1,009.90