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	$173.36	10.788%	$192.0621	$192.06	$192.05	$192.10
Purchase #2	$249.81	11.816%	$279.3275	$279.33	$279.35	$279.30
Purchase #3	$72.34	13.231%	$81.9113	$81.91	$81.90	$81.90
Purchase #4	$198.54	6.207%	$210.8634	$210.86	$210.85	$210.90
Purchase #5	$112.85	13.329%	$127.8918	$127.89	$127.90	$127.90
Purchase #6	$227.92	4.754%	$238.7553	$238.76	$238.75	$238.80
Purchase #7	$122.60	6.509%	$130.58	$130.58	$130.60	$130.60
7 purchase totals =	$1,157.42		$1,261.3914	$1,261.39	$1,261.40	$1,261.50