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	$81.58	11.357%	$90.845	$90.85	$90.85	$90.80
Purchase #2	$79.44	9.132%	$86.6945	$86.69	$86.70	$86.70
Purchase #3	$186.85	7.223%	$200.3462	$200.35	$200.35	$200.30
Purchase #4	$177.86	6.558%	$189.5241	$189.52	$189.50	$189.50
Purchase #5	$233.33	12.239%	$261.8873	$261.89	$261.90	$261.90
Purchase #6	$187.77	5.510%	$198.1161	$198.12	$198.10	$198.10
Purchase #7	$67.46	3.246%	$69.6498	$69.65	$69.65	$69.60
7 purchase totals =	$1,014.29		$1,097.0630	$1,097.07	$1,097.05	$1,096.90