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	$7.86	13.684%	$8.9356	$8.94	$8.95	$8.90
Purchase #2	$145.33	4.578%	$151.9832	$151.98	$152.00	$152.00
Purchase #3	$47.80	10.559%	$52.8472	$52.85	$52.85	$52.80
Purchase #4	$196.39	11.402%	$218.7824	$218.78	$218.80	$218.80
Purchase #5	$98.79	12.451%	$111.0903	$111.09	$111.10	$111.10
Purchase #6	$194.84	10.732%	$215.7502	$215.75	$215.75	$215.80
Purchase #7	$41.82	9.752%	$45.8983	$45.90	$45.90	$45.90
7 purchase totals =	$732.83		$805.2872	$805.29	$805.35	$805.30