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	$228.92	10.241%	$252.3637	$252.36	$252.35	$252.40
Purchase #2	$90.98	13.515%	$103.2759	$103.28	$103.30	$103.30
Purchase #3	$200.97	10.688%	$222.4497	$222.45	$222.45	$222.40
Purchase #4	$225.59	5.598%	$238.2185	$238.22	$238.20	$238.20
Purchase #5	$62.33	8.789%	$67.8082	$67.81	$67.80	$67.80
Purchase #6	$233.46	5.213%	$245.6303	$245.63	$245.65	$245.60
Purchase #7	$24.36	6.291%	$25.8925	$25.89	$25.90	$25.90
7 purchase totals =	$1,066.61		$1,155.6388	$1,155.64	$1,155.65	$1,155.60