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	$24.51	10.694%	$27.1311	$27.13	$27.15	$27.10
Purchase #2	$39.43	11.362%	$43.91	$43.91	$43.90	$43.90
Purchase #3	$205.52	4.641%	$215.0582	$215.06	$215.05	$215.10
Purchase #4	$167.75	12.426%	$188.5946	$188.59	$188.60	$188.60
Purchase #5	$223.48	11.436%	$249.0372	$249.04	$249.05	$249.00
Purchase #6	$144.27	3.188%	$148.8693	$148.87	$148.85	$148.90
Purchase #7	$227.84	11.292%	$253.5677	$253.57	$253.55	$253.60
7 purchase totals =	$1,032.80		$1,126.1681	$1,126.17	$1,126.15	$1,126.20