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	$211.34	12.859%	$238.5162	$238.52	$238.50	$238.50
Purchase #2	$156.66	9.549%	$171.6195	$171.62	$171.60	$171.60
Purchase #3	$132.40	7.676%	$142.563	$142.56	$142.55	$142.60
Purchase #4	$237.57	5.458%	$250.5366	$250.54	$250.55	$250.50
Purchase #5	$79.58	7.535%	$85.5764	$85.58	$85.60	$85.60
Purchase #6	$105.99	6.520%	$112.9005	$112.90	$112.90	$112.90
Purchase #7	$19.64	13.611%	$22.3132	$22.31	$22.30	$22.30
7 purchase totals =	$943.18		$1,024.0254	$1,024.03	$1,024.00	$1,024.00