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	$43.78	4.765%	$45.8661	$45.87	$45.85	$45.90
Purchase #2	$146.25	12.799%	$164.9685	$164.97	$164.95	$165.00
Purchase #3	$132.83	6.397%	$141.3271	$141.33	$141.35	$141.30
Purchase #4	$194.97	10.687%	$215.8064	$215.81	$215.80	$215.80
Purchase #5	$232.83	11.768%	$260.2294	$260.23	$260.25	$260.20
Purchase #6	$67.35	5.292%	$70.9142	$70.91	$70.90	$70.90
Purchase #7	$137.37	5.598%	$145.06	$145.06	$145.05	$145.10
7 purchase totals =	$955.38		$1,044.1717	$1,044.18	$1,044.15	$1,044.20