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	$43.86	6.183%	$46.5719	$46.57	$46.55	$46.60
Purchase #2	$26.30	7.730%	$28.333	$28.33	$28.35	$28.30
Purchase #3	$149.49	8.468%	$162.1488	$162.15	$162.15	$162.10
Purchase #4	$93.34	4.550%	$97.587	$97.59	$97.60	$97.60
Purchase #5	$51.62	3.189%	$53.2662	$53.27	$53.25	$53.30
Purchase #6	$85.45	7.201%	$91.6033	$91.60	$91.60	$91.60
Purchase #7	$175.86	4.358%	$183.524	$183.52	$183.50	$183.50
7 purchase totals =	$625.92		$663.0342	$663.03	$663.00	$663.00