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	$68.80	9.564%	$75.38	$75.38	$75.40	$75.40
Purchase #2	$232.68	11.647%	$259.7802	$259.78	$259.80	$259.80
Purchase #3	$22.32	7.553%	$24.0058	$24.01	$24.00	$24.00
Purchase #4	$102.96	8.440%	$111.6498	$111.65	$111.65	$111.60
Purchase #5	$72.57	13.354%	$82.261	$82.26	$82.25	$82.30
Purchase #6	$200.56	7.656%	$215.9149	$215.91	$215.90	$215.90
Purchase #7	$232.79	13.765%	$264.8335	$264.83	$264.85	$264.80
7 purchase totals =	$932.68		$1,033.8252	$1,033.82	$1,033.85	$1,033.80