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	$126.66	10.707%	$140.2215	$140.22	$140.20	$140.20
Purchase #2	$126.77	12.621%	$142.7696	$142.77	$142.75	$142.80
Purchase #3	$116.43	9.695%	$127.7179	$127.72	$127.70	$127.70
Purchase #4	$166.56	4.524%	$174.0952	$174.10	$174.10	$174.10
Purchase #5	$214.61	5.261%	$225.9006	$225.90	$225.90	$225.90
Purchase #6	$96.99	13.407%	$109.9934	$109.99	$110.00	$110.00
Purchase #7	$163.86	7.518%	$176.179	$176.18	$176.20	$176.20
7 purchase totals =	$1,011.88		$1,096.8772	$1,096.88	$1,096.85	$1,096.90