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	$250.46	5.660%	$264.636	$264.64	$264.65	$264.60
Purchase #2	$178.30	4.644%	$186.5803	$186.58	$186.60	$186.60
Purchase #3	$76.71	9.360%	$83.8901	$83.89	$83.90	$83.90
Purchase #4	$93.48	11.296%	$104.0395	$104.04	$104.05	$104.00
Purchase #5	$134.25	10.441%	$148.267	$148.27	$148.25	$148.30
Purchase #6	$153.27	11.312%	$170.6079	$170.61	$170.60	$170.60
Purchase #7	$138.68	11.405%	$154.4965	$154.50	$154.50	$154.50
7 purchase totals =	$1,025.15		$1,112.5173	$1,112.53	$1,112.55	$1,112.50