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	$28.89	12.801%	$32.5882	$32.59	$32.60	$32.60
Purchase #2	$23.82	5.743%	$25.188	$25.19	$25.20	$25.20
Purchase #3	$237.50	7.871%	$256.1936	$256.19	$256.20	$256.20
Purchase #4	$104.97	4.172%	$109.3493	$109.35	$109.35	$109.30
Purchase #5	$116.52	3.526%	$120.6285	$120.63	$120.65	$120.60
Purchase #6	$164.95	11.688%	$184.2294	$184.23	$184.25	$184.20
Purchase #7	$213.25	9.781%	$234.108	$234.11	$234.10	$234.10
7 purchase totals =	$889.90		$962.2850	$962.29	$962.35	$962.20