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	$100.60	10.759%	$111.4236	$111.42	$111.40	$111.40
Purchase #2	$62.83	7.229%	$67.372	$67.37	$67.35	$67.40
Purchase #3	$131.85	5.741%	$139.4195	$139.42	$139.40	$139.40
Purchase #4	$170.70	12.638%	$192.2731	$192.27	$192.25	$192.30
Purchase #5	$110.63	11.726%	$123.6025	$123.60	$123.60	$123.60
Purchase #6	$161.38	3.330%	$166.754	$166.75	$166.75	$166.80
Purchase #7	$206.31	12.246%	$231.5747	$231.57	$231.55	$231.60
7 purchase totals =	$944.30		$1,032.4194	$1,032.40	$1,032.30	$1,032.50