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	$191.90	13.474%	$217.7566	$217.76	$217.75	$217.80
Purchase #2	$53.94	10.103%	$59.3896	$59.39	$59.40	$59.40
Purchase #3	$135.87	10.801%	$150.5453	$150.55	$150.55	$150.50
Purchase #4	$200.57	11.464%	$223.5633	$223.56	$223.55	$223.60
Purchase #5	$38.72	11.314%	$43.1008	$43.10	$43.10	$43.10
Purchase #6	$212.31	4.500%	$221.864	$221.86	$221.85	$221.90
Purchase #7	$227.30	5.628%	$240.0924	$240.09	$240.10	$240.10
7 purchase totals =	$1,060.61		$1,156.3120	$1,156.31	$1,156.30	$1,156.40