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	$87.55	3.269%	$90.412	$90.41	$90.40	$90.40
Purchase #2	$108.92	5.269%	$114.659	$114.66	$114.65	$114.70
Purchase #3	$160.66	4.234%	$167.4623	$167.46	$167.45	$167.50
Purchase #4	$164.63	13.107%	$186.2081	$186.21	$186.20	$186.20
Purchase #5	$47.74	11.134%	$53.0554	$53.06	$53.05	$53.10
Purchase #6	$85.30	6.308%	$90.6807	$90.68	$90.70	$90.70
Purchase #7	$177.34	10.126%	$195.2974	$195.30	$195.30	$195.30
7 purchase totals =	$832.14		$897.7749	$897.78	$897.75	$897.90