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	$55.75	11.805%	$62.3313	$62.33	$62.35	$62.30
Purchase #2	$167.28	7.847%	$180.4065	$180.41	$180.40	$180.40
Purchase #3	$20.69	8.257%	$22.3984	$22.40	$22.40	$22.40
Purchase #4	$179.51	6.158%	$190.5642	$190.56	$190.55	$190.60
Purchase #5	$206.36	4.612%	$215.8773	$215.88	$215.90	$215.90
Purchase #6	$104.94	9.456%	$114.8631	$114.86	$114.85	$114.90
Purchase #7	$176.84	13.609%	$200.9062	$200.91	$200.90	$200.90
7 purchase totals =	$911.37		$987.3470	$987.35	$987.35	$987.40