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	$138.93	13.157%	$157.209	$157.21	$157.20	$157.20
Purchase #2	$211.98	5.480%	$223.5965	$223.60	$223.60	$223.60
Purchase #3	$156.95	9.217%	$171.4161	$171.42	$171.40	$171.40
Purchase #4	$164.49	6.197%	$174.6834	$174.68	$174.70	$174.70
Purchase #5	$68.69	5.855%	$72.7118	$72.71	$72.70	$72.70
Purchase #6	$63.37	6.123%	$67.2501	$67.25	$67.25	$67.30
Purchase #7	$182.75	3.271%	$188.7278	$188.73	$188.75	$188.70
7 purchase totals =	$987.16		$1,055.5947	$1,055.60	$1,055.60	$1,055.60