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	$140.55	11.329%	$156.4729	$156.47	$156.45	$156.50
Purchase #2	$47.32	12.338%	$53.1583	$53.16	$53.15	$53.20
Purchase #3	$186.75	5.385%	$196.8065	$196.81	$196.80	$196.80
Purchase #4	$65.25	9.793%	$71.6399	$71.64	$71.65	$71.60
Purchase #5	$79.54	5.295%	$83.7516	$83.75	$83.75	$83.80
Purchase #6	$203.44	11.611%	$227.0614	$227.06	$227.05	$227.10
Purchase #7	$230.56	8.626%	$250.4481	$250.45	$250.45	$250.40
7 purchase totals =	$953.41		$1,039.3387	$1,039.34	$1,039.30	$1,039.40