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	$77.98	12.121%	$87.432	$87.43	$87.45	$87.40
Purchase #2	$164.85	6.373%	$175.3559	$175.36	$175.35	$175.40
Purchase #3	$52.59	4.378%	$54.8924	$54.89	$54.90	$54.90
Purchase #4	$72.74	12.189%	$81.6063	$81.61	$81.60	$81.60
Purchase #5	$138.96	12.862%	$156.833	$156.83	$156.85	$156.80
Purchase #6	$140.73	5.620%	$148.639	$148.64	$148.65	$148.60
Purchase #7	$75.55	3.461%	$78.1648	$78.16	$78.15	$78.20
7 purchase totals =	$723.40		$782.9234	$782.92	$782.95	$782.90