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	$182.27	9.108%	$198.8712	$198.87	$198.85	$198.90
Purchase #2	$177.91	10.653%	$196.8628	$196.86	$196.85	$196.90
Purchase #3	$145.71	6.778%	$155.5862	$155.59	$155.60	$155.60
Purchase #4	$31.96	12.737%	$36.0307	$36.03	$36.05	$36.00
Purchase #5	$233.81	12.460%	$262.9427	$262.94	$262.95	$262.90
Purchase #6	$179.42	3.527%	$185.7481	$185.75	$185.75	$185.70
Purchase #7	$160.42	10.689%	$177.5673	$177.57	$177.55	$177.60
7 purchase totals =	$1,111.50		$1,213.6090	$1,213.61	$1,213.60	$1,213.60