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	$220.46	9.156%	$240.6453	$240.65	$240.65	$240.60
Purchase #2	$76.33	5.554%	$80.5694	$80.57	$80.55	$80.60
Purchase #3	$109.82	12.555%	$123.6079	$123.61	$123.60	$123.60
Purchase #4	$142.81	11.727%	$159.5573	$159.56	$159.55	$159.60
Purchase #5	$249.32	6.813%	$266.3062	$266.31	$266.30	$266.30
Purchase #6	$146.56	5.308%	$154.3394	$154.34	$154.35	$154.30
Purchase #7	$174.82	8.718%	$190.0608	$190.06	$190.05	$190.10
7 purchase totals =	$1,120.12		$1,215.0863	$1,215.10	$1,215.05	$1,215.10