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	$131.39	7.192%	$140.8396	$140.84	$140.85	$140.80
Purchase #2	$174.67	10.715%	$193.3859	$193.39	$193.40	$193.40
Purchase #3	$148.84	5.389%	$156.861	$156.86	$156.85	$156.90
Purchase #4	$83.50	8.752%	$90.8079	$90.81	$90.80	$90.80
Purchase #5	$87.87	13.840%	$100.0312	$100.03	$100.05	$100.00
Purchase #6	$103.50	13.391%	$117.3597	$117.36	$117.35	$117.40
Purchase #7	$223.45	8.353%	$242.1148	$242.11	$242.10	$242.10
7 purchase totals =	$953.22		$1,041.4001	$1,041.40	$1,041.40	$1,041.40