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	$245.94	3.760%	$255.1873	$255.19	$255.20	$255.20
Purchase #2	$84.82	12.736%	$95.6227	$95.62	$95.60	$95.60
Purchase #3	$189.48	5.592%	$200.0757	$200.08	$200.10	$200.10
Purchase #4	$97.55	9.223%	$106.547	$106.55	$106.55	$106.50
Purchase #5	$27.89	12.342%	$31.3322	$31.33	$31.35	$31.30
Purchase #6	$220.45	6.158%	$234.0253	$234.03	$234.05	$234.00
Purchase #7	$137.41	5.246%	$144.6185	$144.62	$144.60	$144.60
7 purchase totals =	$1,003.54		$1,067.4087	$1,067.42	$1,067.45	$1,067.30