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	$227.40	9.297%	$248.5414	$248.54	$248.55	$248.50
Purchase #2	$213.97	7.456%	$229.9236	$229.92	$229.90	$229.90
Purchase #3	$39.30	10.795%	$43.5424	$43.54	$43.55	$43.50
Purchase #4	$234.62	4.420%	$244.9902	$244.99	$245.00	$245.00
Purchase #5	$130.88	8.807%	$142.4066	$142.41	$142.40	$142.40
Purchase #6	$100.65	5.827%	$106.5149	$106.51	$106.50	$106.50
Purchase #7	$128.61	12.333%	$144.4715	$144.47	$144.45	$144.50
7 purchase totals =	$1,075.43		$1,160.3906	$1,160.38	$1,160.35	$1,160.30