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	$147.76	11.570%	$164.8558	$164.86	$164.85	$164.90
Purchase #2	$238.81	11.333%	$265.8743	$265.87	$265.85	$265.90
Purchase #3	$81.33	10.520%	$89.8859	$89.89	$89.90	$89.90
Purchase #4	$134.37	6.312%	$142.8514	$142.85	$142.85	$142.90
Purchase #5	$33.87	6.563%	$36.0929	$36.09	$36.10	$36.10
Purchase #6	$72.57	10.420%	$80.1318	$80.13	$80.15	$80.10
Purchase #7	$214.64	4.771%	$224.8805	$224.88	$224.90	$224.90
7 purchase totals =	$923.35		$1,004.5726	$1,004.57	$1,004.60	$1,004.70