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	$20.98	4.630%	$21.9514	$21.95	$21.95	$22.00
Purchase #2	$69.94	3.872%	$72.6481	$72.65	$72.65	$72.60
Purchase #3	$25.78	6.521%	$27.4611	$27.46	$27.45	$27.50
Purchase #4	$103.40	10.580%	$114.3397	$114.34	$114.35	$114.30
Purchase #5	$18.81	7.611%	$20.2416	$20.24	$20.25	$20.20
Purchase #6	$125.79	4.443%	$131.3788	$131.38	$131.40	$131.40
Purchase #7	$179.80	8.696%	$195.4354	$195.44	$195.45	$195.40
7 purchase totals =	$544.50		$583.4561	$583.46	$583.50	$583.40