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	$224.94	4.284%	$234.5764	$234.58	$234.60	$234.60
Purchase #2	$162.64	11.719%	$181.6998	$181.70	$181.70	$181.70
Purchase #3	$106.25	3.696%	$110.177	$110.18	$110.20	$110.20
Purchase #4	$160.84	4.488%	$168.0585	$168.06	$168.05	$168.10
Purchase #5	$101.32	10.436%	$111.8938	$111.89	$111.90	$111.90
Purchase #6	$82.37	9.780%	$90.4258	$90.43	$90.45	$90.40
Purchase #7	$40.97	12.777%	$46.2047	$46.20	$46.20	$46.20
7 purchase totals =	$879.33		$943.0360	$943.04	$943.10	$943.10