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	$103.68	11.637%	$115.7452	$115.75	$115.75	$115.70
Purchase #2	$77.57	6.784%	$82.8323	$82.83	$82.85	$82.80
Purchase #3	$86.41	9.725%	$94.8134	$94.81	$94.80	$94.80
Purchase #4	$180.58	11.226%	$200.8519	$200.85	$200.85	$200.90
Purchase #5	$238.82	7.637%	$257.0587	$257.06	$257.05	$257.10
Purchase #6	$54.33	4.706%	$56.8868	$56.89	$56.90	$56.90
Purchase #7	$94.88	4.146%	$98.8137	$98.81	$98.80	$98.80
7 purchase totals =	$836.27		$907.0020	$907.00	$907.00	$907.00