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	$92.80	7.178%	$99.4612	$99.46	$99.45	$99.50
Purchase #2	$198.34	7.430%	$213.0767	$213.08	$213.10	$213.10
Purchase #3	$242.60	5.310%	$255.4821	$255.48	$255.50	$255.50
Purchase #4	$44.76	8.241%	$48.4487	$48.45	$48.45	$48.40
Purchase #5	$114.75	9.164%	$125.2657	$125.27	$125.25	$125.30
Purchase #6	$94.71	9.267%	$103.4868	$103.49	$103.50	$103.50
Purchase #7	$109.97	12.344%	$123.5447	$123.54	$123.55	$123.50
7 purchase totals =	$897.93		$968.7659	$968.77	$968.80	$968.80