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	$238.28	4.697%	$249.472	$249.47	$249.45	$249.50
Purchase #2	$77.54	9.736%	$85.0893	$85.09	$85.10	$85.10
Purchase #3	$73.61	7.403%	$79.0593	$79.06	$79.05	$79.10
Purchase #4	$222.41	12.659%	$250.5649	$250.56	$250.55	$250.60
Purchase #5	$9.58	12.524%	$10.7798	$10.78	$10.80	$10.80
Purchase #6	$162.70	7.796%	$175.3841	$175.38	$175.40	$175.40
Purchase #7	$154.92	7.177%	$166.0386	$166.04	$166.05	$166.00
7 purchase totals =	$939.04		$1,016.3880	$1,016.38	$1,016.40	$1,016.50