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	$114.90	10.671%	$127.161	$127.16	$127.15	$127.20
Purchase #2	$181.35	11.558%	$202.3104	$202.31	$202.30	$202.30
Purchase #3	$113.86	11.739%	$127.226	$127.23	$127.25	$127.20
Purchase #4	$5.86	9.449%	$6.4137	$6.41	$6.40	$6.40
Purchase #5	$203.61	10.299%	$224.5798	$224.58	$224.60	$224.60
Purchase #6	$133.62	6.193%	$141.8951	$141.90	$141.90	$141.90
Purchase #7	$97.85	5.138%	$102.8775	$102.88	$102.90	$102.90
7 purchase totals =	$851.05		$932.4635	$932.47	$932.50	$932.50