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	$187.47	6.745%	$200.1149	$200.11	$200.10	$200.10
Purchase #2	$235.83	5.114%	$247.8903	$247.89	$247.90	$247.90
Purchase #3	$97.70	5.307%	$102.8849	$102.88	$102.90	$102.90
Purchase #4	$13.87	10.462%	$15.3211	$15.32	$15.30	$15.30
Purchase #5	$158.42	13.823%	$180.3184	$180.32	$180.30	$180.30
Purchase #6	$165.36	12.552%	$186.116	$186.12	$186.10	$186.10
Purchase #7	$49.67	9.730%	$54.5029	$54.50	$54.50	$54.50
7 purchase totals =	$908.32		$987.1485	$987.14	$987.10	$987.10