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	$208.49	11.864%	$233.2253	$233.23	$233.25	$233.20
Purchase #2	$79.96	13.267%	$90.5683	$90.57	$90.55	$90.60
Purchase #3	$230.36	11.515%	$256.886	$256.89	$256.90	$256.90
Purchase #4	$39.32	9.515%	$43.0613	$43.06	$43.05	$43.10
Purchase #5	$160.35	4.787%	$168.026	$168.03	$168.05	$168.00
Purchase #6	$227.55	5.460%	$239.9742	$239.97	$239.95	$240.00
Purchase #7	$17.90	10.628%	$19.8024	$19.80	$19.80	$19.80
7 purchase totals =	$963.93		$1,051.5435	$1,051.55	$1,051.55	$1,051.60