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	$52.37	13.512%	$59.4462	$59.45	$59.45	$59.40
Purchase #2	$100.69	10.467%	$111.2292	$111.23	$111.25	$111.20
Purchase #3	$29.38	10.724%	$32.5307	$32.53	$32.55	$32.50
Purchase #4	$33.51	7.800%	$36.1238	$36.12	$36.10	$36.10
Purchase #5	$201.59	3.670%	$208.9884	$208.99	$209.00	$209.00
Purchase #6	$178.49	11.822%	$199.5911	$199.59	$199.60	$199.60
Purchase #7	$100.27	12.735%	$113.0394	$113.04	$113.05	$113.00
7 purchase totals =	$696.30		$760.9488	$760.95	$761.00	$760.80