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	$206.52	11.166%	$229.58	$229.58	$229.60	$229.60
Purchase #2	$242.41	13.671%	$275.5499	$275.55	$275.55	$275.50
Purchase #3	$91.80	6.156%	$97.4512	$97.45	$97.45	$97.50
Purchase #4	$148.29	8.337%	$160.6529	$160.65	$160.65	$160.70
Purchase #5	$210.82	13.785%	$239.8815	$239.88	$239.90	$239.90
Purchase #6	$116.37	6.454%	$123.8805	$123.88	$123.90	$123.90
Purchase #7	$241.82	13.655%	$274.8405	$274.84	$274.85	$274.80
7 purchase totals =	$1,258.03		$1,401.8365	$1,401.83	$1,401.90	$1,401.90