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	$250.28	11.498%	$279.0572	$279.06	$279.05	$279.10
Purchase #2	$7.54	11.441%	$8.4027	$8.40	$8.40	$8.40
Purchase #3	$156.38	6.737%	$166.9153	$166.92	$166.90	$166.90
Purchase #4	$76.37	5.300%	$80.4176	$80.42	$80.40	$80.40
Purchase #5	$52.91	7.355%	$56.8015	$56.80	$56.80	$56.80
Purchase #6	$225.26	9.468%	$246.5876	$246.59	$246.60	$246.60
Purchase #7	$207.40	7.526%	$223.0089	$223.01	$223.00	$223.00
7 purchase totals =	$976.14		$1,061.1908	$1,061.20	$1,061.15	$1,061.20