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	$154.99	8.143%	$167.6108	$167.61	$167.60	$167.60
Purchase #2	$49.63	11.290%	$55.2332	$55.23	$55.25	$55.20
Purchase #3	$159.89	5.218%	$168.2331	$168.23	$168.25	$168.20
Purchase #4	$123.88	5.737%	$130.987	$130.99	$131.00	$131.00
Purchase #5	$206.72	4.277%	$215.5614	$215.56	$215.55	$215.60
Purchase #6	$184.49	9.541%	$202.0922	$202.09	$202.10	$202.10
Purchase #7	$234.89	9.139%	$256.3566	$256.36	$256.35	$256.40
7 purchase totals =	$1,114.49		$1,196.0743	$1,196.07	$1,196.10	$1,196.10