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	$101.88	11.544%	$113.641	$113.64	$113.65	$113.60
Purchase #2	$76.58	9.162%	$83.5963	$83.60	$83.60	$83.60
Purchase #3	$122.89	3.654%	$127.3804	$127.38	$127.40	$127.40
Purchase #4	$203.47	6.430%	$216.5531	$216.55	$216.55	$216.60
Purchase #5	$242.84	13.609%	$275.8881	$275.89	$275.90	$275.90
Purchase #6	$226.36	6.597%	$241.293	$241.29	$241.30	$241.30
Purchase #7	$47.92	8.316%	$51.905	$51.91	$51.90	$51.90
7 purchase totals =	$1,021.94		$1,110.2569	$1,110.26	$1,110.30	$1,110.30