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	$44.58	6.756%	$47.5918	$47.59	$47.60	$47.60
Purchase #2	$241.69	7.780%	$260.4935	$260.49	$260.50	$260.50
Purchase #3	$48.60	12.215%	$54.5365	$54.54	$54.55	$54.50
Purchase #4	$64.68	12.269%	$72.6156	$72.62	$72.60	$72.60
Purchase #5	$119.36	12.645%	$134.4531	$134.45	$134.45	$134.50
Purchase #6	$78.45	10.130%	$86.397	$86.40	$86.40	$86.40
Purchase #7	$242.98	10.811%	$269.2486	$269.25	$269.25	$269.20
7 purchase totals =	$840.34		$925.3361	$925.34	$925.35	$925.30