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	$194.93	11.156%	$216.6764	$216.68	$216.70	$216.70
Purchase #2	$231.78	4.872%	$243.0723	$243.07	$243.05	$243.10
Purchase #3	$102.56	10.320%	$113.1442	$113.14	$113.15	$113.10
Purchase #4	$181.36	13.208%	$205.314	$205.31	$205.30	$205.30
Purchase #5	$65.78	8.477%	$71.3562	$71.36	$71.35	$71.40
Purchase #6	$64.57	13.257%	$73.13	$73.13	$73.15	$73.10
Purchase #7	$73.64	6.716%	$78.5857	$78.59	$78.60	$78.60
7 purchase totals =	$914.62		$1,001.2788	$1,001.28	$1,001.30	$1,001.30