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	$88.49	4.173%	$92.1827	$92.18	$92.20	$92.20
Purchase #2	$208.89	6.588%	$222.6517	$222.65	$222.65	$222.70
Purchase #3	$63.91	5.668%	$67.5324	$67.53	$67.55	$67.50
Purchase #4	$164.34	13.503%	$186.5308	$186.53	$186.55	$186.50
Purchase #5	$127.28	13.308%	$144.2184	$144.22	$144.20	$144.20
Purchase #6	$121.45	6.595%	$129.4596	$129.46	$129.45	$129.50
Purchase #7	$115.59	3.689%	$119.8541	$119.85	$119.85	$119.90
7 purchase totals =	$889.95		$962.4297	$962.42	$962.45	$962.50