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	$54.57	8.747%	$59.3432	$59.34	$59.35	$59.30
Purchase #2	$151.74	6.139%	$161.0553	$161.06	$161.05	$161.10
Purchase #3	$38.97	10.469%	$43.0498	$43.05	$43.05	$43.00
Purchase #4	$205.57	13.301%	$232.9129	$232.91	$232.90	$232.90
Purchase #5	$120.86	6.398%	$128.5926	$128.59	$128.60	$128.60
Purchase #6	$66.56	8.452%	$72.1857	$72.19	$72.20	$72.20
Purchase #7	$43.69	6.321%	$46.4516	$46.45	$46.45	$46.50
7 purchase totals =	$681.96		$743.5911	$743.59	$743.60	$743.60