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	$129.83	9.191%	$141.7627	$141.76	$141.75	$141.80
Purchase #2	$205.61	4.482%	$214.8254	$214.83	$214.85	$214.80
Purchase #3	$81.40	12.528%	$91.5978	$91.60	$91.60	$91.60
Purchase #4	$78.71	9.364%	$86.0804	$86.08	$86.10	$86.10
Purchase #5	$33.88	8.681%	$36.8211	$36.82	$36.80	$36.80
Purchase #6	$190.61	6.807%	$203.5848	$203.58	$203.60	$203.60
Purchase #7	$213.76	13.296%	$242.1815	$242.18	$242.20	$242.20
7 purchase totals =	$933.80		$1,016.8537	$1,016.85	$1,016.90	$1,016.90