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	$101.59	3.841%	$105.4921	$105.49	$105.50	$105.50
Purchase #2	$230.89	4.709%	$241.7626	$241.76	$241.75	$241.80
Purchase #3	$194.65	4.792%	$203.9776	$203.98	$204.00	$204.00
Purchase #4	$71.90	6.654%	$76.6842	$76.68	$76.70	$76.70
Purchase #5	$94.41	4.714%	$98.8605	$98.86	$98.85	$98.90
Purchase #6	$160.43	13.579%	$182.2148	$182.21	$182.20	$182.20
Purchase #7	$156.41	13.490%	$177.5097	$177.51	$177.50	$177.50
7 purchase totals =	$1,010.28		$1,086.5015	$1,086.49	$1,086.50	$1,086.60