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	$81.67	10.838%	$90.5214	$90.52	$90.50	$90.50
Purchase #2	$114.56	8.401%	$124.1842	$124.18	$124.20	$124.20
Purchase #3	$6.64	7.664%	$7.1489	$7.15	$7.15	$7.10
Purchase #4	$242.82	6.630%	$258.919	$258.92	$258.90	$258.90
Purchase #5	$239.77	4.536%	$250.646	$250.65	$250.65	$250.60
Purchase #6	$201.67	11.762%	$225.3904	$225.39	$225.40	$225.40
Purchase #7	$115.47	12.212%	$129.5712	$129.57	$129.55	$129.60
7 purchase totals =	$1,002.60		$1,086.3811	$1,086.38	$1,086.35	$1,086.30