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	$79.64	7.807%	$85.8575	$85.86	$85.85	$85.90
Purchase #2	$233.59	10.408%	$257.902	$257.90	$257.90	$257.90
Purchase #3	$225.55	4.288%	$235.2216	$235.22	$235.20	$235.20
Purchase #4	$93.89	8.260%	$101.6453	$101.65	$101.65	$101.60
Purchase #5	$112.27	3.703%	$116.4274	$116.43	$116.45	$116.40
Purchase #6	$139.46	11.727%	$155.8145	$155.81	$155.80	$155.80
Purchase #7	$46.53	4.260%	$48.5122	$48.51	$48.50	$48.50
7 purchase totals =	$930.93		$1,001.3805	$1,001.38	$1,001.35	$1,001.30