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	$114.78	3.588%	$118.8983	$118.90	$118.90	$118.90
Purchase #2	$164.71	12.691%	$185.6133	$185.61	$185.60	$185.60
Purchase #3	$130.96	11.283%	$145.7362	$145.74	$145.75	$145.70
Purchase #4	$53.97	13.260%	$61.1264	$61.13	$61.15	$61.10
Purchase #5	$13.92	3.214%	$14.3674	$14.37	$14.35	$14.40
Purchase #6	$156.33	5.435%	$164.8265	$164.83	$164.85	$164.80
Purchase #7	$68.75	13.161%	$77.7982	$77.80	$77.80	$77.80
7 purchase totals =	$703.42		$768.3663	$768.38	$768.40	$768.30