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	$63.49	5.625%	$67.0613	$67.06	$67.05	$67.10
Purchase #2	$242.60	7.102%	$259.8295	$259.83	$259.85	$259.80
Purchase #3	$71.98	9.152%	$78.5676	$78.57	$78.55	$78.60
Purchase #4	$134.76	12.850%	$152.0767	$152.08	$152.10	$152.10
Purchase #5	$186.53	6.411%	$198.4884	$198.49	$198.50	$198.50
Purchase #6	$227.28	8.448%	$246.4806	$246.48	$246.50	$246.50
Purchase #7	$249.28	11.633%	$278.2787	$278.28	$278.30	$278.30
7 purchase totals =	$1,175.92		$1,280.7828	$1,280.79	$1,280.85	$1,280.90