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	$230.43	10.304%	$254.1735	$254.17	$254.15	$254.20
Purchase #2	$65.93	7.701%	$71.0073	$71.01	$71.00	$71.00
Purchase #3	$169.42	9.553%	$185.6047	$185.60	$185.60	$185.60
Purchase #4	$160.72	7.468%	$172.7226	$172.72	$172.70	$172.70
Purchase #5	$133.80	11.680%	$149.4278	$149.43	$149.45	$149.40
Purchase #6	$84.69	9.656%	$92.8677	$92.87	$92.85	$92.90
Purchase #7	$119.59	12.745%	$134.8317	$134.83	$134.85	$134.80
7 purchase totals =	$964.58		$1,060.6353	$1,060.63	$1,060.60	$1,060.60