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	$190.58	11.333%	$212.1784	$212.18	$212.20	$212.20
Purchase #2	$66.48	12.607%	$74.8611	$74.86	$74.85	$74.90
Purchase #3	$97.50	12.687%	$109.8698	$109.87	$109.85	$109.90
Purchase #4	$85.63	4.354%	$89.3583	$89.36	$89.35	$89.40
Purchase #5	$146.82	9.259%	$160.4141	$160.41	$160.40	$160.40
Purchase #6	$109.77	7.726%	$118.2508	$118.25	$118.25	$118.30
Purchase #7	$14.64	8.162%	$15.8349	$15.83	$15.85	$15.80
7 purchase totals =	$711.42		$780.7674	$780.76	$780.75	$780.90