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	$243.27	5.243%	$256.0246	$256.02	$256.00	$256.00
Purchase #2	$66.31	11.218%	$73.7487	$73.75	$73.75	$73.70
Purchase #3	$56.61	12.852%	$63.8855	$63.89	$63.90	$63.90
Purchase #4	$77.79	6.209%	$82.62	$82.62	$82.60	$82.60
Purchase #5	$81.89	4.550%	$85.616	$85.62	$85.60	$85.60
Purchase #6	$42.72	5.565%	$45.0974	$45.10	$45.10	$45.10
Purchase #7	$164.79	7.663%	$177.4179	$177.42	$177.40	$177.40
7 purchase totals =	$733.38		$784.4101	$784.42	$784.35	$784.30