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	$248.78	5.554%	$262.5972	$262.60	$262.60	$262.60
Purchase #2	$89.80	6.428%	$95.5723	$95.57	$95.55	$95.60
Purchase #3	$71.33	10.365%	$78.7234	$78.72	$78.70	$78.70
Purchase #4	$114.49	3.766%	$118.8017	$118.80	$118.80	$118.80
Purchase #5	$199.54	10.265%	$220.0228	$220.02	$220.00	$220.00
Purchase #6	$75.89	13.461%	$86.1056	$86.11	$86.10	$86.10
Purchase #7	$227.62	9.756%	$249.8266	$249.83	$249.85	$249.80
7 purchase totals =	$1,027.45		$1,111.6496	$1,111.65	$1,111.60	$1,111.60