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	$116.37	3.765%	$120.7513	$120.75	$120.75	$120.80
Purchase #2	$128.58	3.329%	$132.8604	$132.86	$132.85	$132.90
Purchase #3	$162.88	13.814%	$185.3802	$185.38	$185.40	$185.40
Purchase #4	$93.66	7.672%	$100.8456	$100.85	$100.85	$100.80
Purchase #5	$153.99	5.383%	$162.2793	$162.28	$162.30	$162.30
Purchase #6	$174.90	13.727%	$198.9085	$198.91	$198.90	$198.90
Purchase #7	$103.30	10.298%	$113.9378	$113.94	$113.95	$113.90
7 purchase totals =	$933.68		$1,014.9631	$1,014.97	$1,015.00	$1,015.00