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	$120.71	3.110%	$124.4641	$124.46	$124.45	$124.50
Purchase #2	$119.97	11.248%	$133.4642	$133.46	$133.45	$133.50
Purchase #3	$111.91	10.139%	$123.2566	$123.26	$123.25	$123.30
Purchase #4	$19.88	8.404%	$21.5507	$21.55	$21.55	$21.60
Purchase #5	$111.76	7.394%	$120.0235	$120.02	$120.00	$120.00
Purchase #6	$184.63	13.866%	$210.2308	$210.23	$210.25	$210.20
Purchase #7	$19.38	13.285%	$21.9546	$21.95	$21.95	$22.00
7 purchase totals =	$688.24		$754.9445	$754.93	$754.90	$755.10