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	$57.98	9.493%	$63.484	$63.48	$63.50	$63.50
Purchase #2	$24.94	8.651%	$27.0976	$27.10	$27.10	$27.10
Purchase #3	$185.57	3.383%	$191.8478	$191.85	$191.85	$191.80
Purchase #4	$247.48	10.634%	$273.797	$273.80	$273.80	$273.80
Purchase #5	$69.54	13.349%	$78.8229	$78.82	$78.80	$78.80
Purchase #6	$222.42	12.662%	$250.5828	$250.58	$250.60	$250.60
Purchase #7	$110.76	3.351%	$114.4716	$114.47	$114.45	$114.50
7 purchase totals =	$918.69		$1,000.1037	$1,000.10	$1,000.10	$1,000.10