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	$237.63	9.764%	$260.8322	$260.83	$260.85	$260.80
Purchase #2	$138.72	9.423%	$151.7916	$151.79	$151.80	$151.80
Purchase #3	$215.47	10.623%	$238.3594	$238.36	$238.35	$238.40
Purchase #4	$74.57	10.737%	$82.5766	$82.58	$82.60	$82.60
Purchase #5	$160.38	4.651%	$167.8393	$167.84	$167.85	$167.80
Purchase #6	$66.43	7.172%	$71.1944	$71.19	$71.20	$71.20
Purchase #7	$40.97	8.155%	$44.3111	$44.31	$44.30	$44.30
7 purchase totals =	$934.17		$1,016.9046	$1,016.90	$1,016.95	$1,016.90