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	$228.69	7.698%	$246.2946	$246.29	$246.30	$246.30
Purchase #2	$73.94	6.108%	$78.4563	$78.46	$78.45	$78.50
Purchase #3	$10.59	12.539%	$11.9179	$11.92	$11.90	$11.90
Purchase #4	$160.52	7.495%	$172.551	$172.55	$172.55	$172.60
Purchase #5	$24.90	9.781%	$27.3355	$27.34	$27.35	$27.30
Purchase #6	$227.98	12.368%	$256.1766	$256.18	$256.20	$256.20
Purchase #7	$49.33	12.140%	$55.3187	$55.32	$55.30	$55.30
7 purchase totals =	$775.95		$848.0506	$848.06	$848.05	$848.10