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	$62.33	10.403%	$68.8142	$68.81	$68.80	$68.80
Purchase #2	$139.66	7.715%	$150.4348	$150.43	$150.45	$150.40
Purchase #3	$86.70	13.681%	$98.5614	$98.56	$98.55	$98.60
Purchase #4	$105.40	5.467%	$111.1622	$111.16	$111.15	$111.20
Purchase #5	$169.40	3.181%	$174.7886	$174.79	$174.80	$174.80
Purchase #6	$227.37	5.813%	$240.587	$240.59	$240.60	$240.60
Purchase #7	$86.65	5.786%	$91.6636	$91.66	$91.65	$91.70
7 purchase totals =	$877.51		$936.0118	$936.00	$936.00	$936.10