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	$240.85	7.220%	$258.2394	$258.24	$258.25	$258.20
Purchase #2	$46.77	3.701%	$48.501	$48.50	$48.50	$48.50
Purchase #3	$130.45	10.110%	$143.6385	$143.64	$143.65	$143.60
Purchase #4	$41.57	5.320%	$43.7815	$43.78	$43.80	$43.80
Purchase #5	$228.56	13.165%	$258.6499	$258.65	$258.65	$258.60
Purchase #6	$158.62	8.185%	$171.603	$171.60	$171.60	$171.60
Purchase #7	$133.77	13.787%	$152.2129	$152.21	$152.20	$152.20
7 purchase totals =	$980.59		$1,076.6262	$1,076.62	$1,076.65	$1,076.50