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	$222.70	7.484%	$239.3669	$239.37	$239.35	$239.40
Purchase #2	$65.84	10.233%	$72.5774	$72.58	$72.60	$72.60
Purchase #3	$95.56	4.469%	$99.8306	$99.83	$99.85	$99.80
Purchase #4	$193.52	6.708%	$206.5013	$206.50	$206.50	$206.50
Purchase #5	$190.69	8.741%	$207.3582	$207.36	$207.35	$207.40
Purchase #6	$57.42	6.340%	$61.0604	$61.06	$61.05	$61.10
Purchase #7	$35.33	11.860%	$39.5201	$39.52	$39.50	$39.50
7 purchase totals =	$861.06		$926.2149	$926.22	$926.20	$926.30