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	$199.76	4.832%	$209.4124	$209.41	$209.40	$209.40
Purchase #2	$59.82	4.280%	$62.3803	$62.38	$62.40	$62.40
Purchase #3	$157.27	3.141%	$162.2099	$162.21	$162.20	$162.20
Purchase #4	$117.35	9.461%	$128.4525	$128.45	$128.45	$128.50
Purchase #5	$78.31	12.123%	$87.8035	$87.80	$87.80	$87.80
Purchase #6	$156.72	5.580%	$165.465	$165.47	$165.45	$165.50
Purchase #7	$210.45	6.836%	$224.8364	$224.84	$224.85	$224.80
7 purchase totals =	$979.68		$1,040.5600	$1,040.56	$1,040.55	$1,040.60