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	$212.69	4.859%	$223.0246	$223.02	$223.00	$223.00
Purchase #2	$117.44	5.716%	$124.1529	$124.15	$124.15	$124.20
Purchase #3	$196.38	10.425%	$216.8526	$216.85	$216.85	$216.90
Purchase #4	$39.94	6.630%	$42.588	$42.59	$42.60	$42.60
Purchase #5	$240.87	10.246%	$265.5495	$265.55	$265.55	$265.50
Purchase #6	$63.59	4.315%	$66.3339	$66.33	$66.35	$66.30
Purchase #7	$122.64	11.629%	$136.9018	$136.90	$136.90	$136.90
7 purchase totals =	$993.55		$1,075.4033	$1,075.39	$1,075.40	$1,075.40