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	$240.76	11.119%	$267.5301	$267.53	$267.55	$267.50
Purchase #2	$60.55	12.716%	$68.2495	$68.25	$68.25	$68.20
Purchase #3	$100.65	4.766%	$105.447	$105.45	$105.45	$105.40
Purchase #4	$153.86	5.529%	$162.3669	$162.37	$162.35	$162.40
Purchase #5	$31.73	4.163%	$33.0509	$33.05	$33.05	$33.10
Purchase #6	$81.75	3.406%	$84.5344	$84.53	$84.55	$84.50
Purchase #7	$59.32	9.833%	$65.1529	$65.15	$65.15	$65.20
7 purchase totals =	$728.62		$786.3317	$786.33	$786.35	$786.30