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	$36.47	10.567%	$40.3238	$40.32	$40.30	$40.30
Purchase #2	$105.38	6.117%	$111.8261	$111.83	$111.85	$111.80
Purchase #3	$187.39	11.110%	$208.209	$208.21	$208.20	$208.20
Purchase #4	$206.62	4.486%	$215.889	$215.89	$215.90	$215.90
Purchase #5	$167.72	4.173%	$174.719	$174.72	$174.70	$174.70
Purchase #6	$43.45	11.548%	$48.4676	$48.47	$48.45	$48.50
Purchase #7	$225.73	10.645%	$249.759	$249.76	$249.75	$249.80
7 purchase totals =	$972.76		$1,049.1935	$1,049.20	$1,049.15	$1,049.20