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	$168.97	8.642%	$183.5724	$183.57	$183.55	$183.60
Purchase #2	$72.42	13.247%	$82.0135	$82.01	$82.00	$82.00
Purchase #3	$97.91	9.104%	$106.8237	$106.82	$106.80	$106.80
Purchase #4	$85.81	9.579%	$94.0297	$94.03	$94.05	$94.00
Purchase #5	$24.59	13.251%	$27.8484	$27.85	$27.85	$27.80
Purchase #6	$168.93	5.788%	$178.7077	$178.71	$178.70	$178.70
Purchase #7	$118.55	4.150%	$123.4698	$123.47	$123.45	$123.50
7 purchase totals =	$737.18		$796.4652	$796.46	$796.40	$796.40