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	$61.82	9.556%	$67.7275	$67.73	$67.75	$67.70
Purchase #2	$99.90	12.202%	$112.0898	$112.09	$112.10	$112.10
Purchase #3	$215.28	11.307%	$239.6217	$239.62	$239.60	$239.60
Purchase #4	$212.60	12.664%	$239.5237	$239.52	$239.50	$239.50
Purchase #5	$135.48	10.837%	$150.162	$150.16	$150.15	$150.20
Purchase #6	$57.98	5.628%	$61.2431	$61.24	$61.25	$61.20
Purchase #7	$64.78	3.657%	$67.149	$67.15	$67.15	$67.10
7 purchase totals =	$847.84		$937.5168	$937.51	$937.50	$937.40