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	$138.46	10.361%	$152.8058	$152.81	$152.80	$152.80
Purchase #2	$14.30	3.656%	$14.8228	$14.82	$14.80	$14.80
Purchase #3	$152.44	9.107%	$166.3227	$166.32	$166.30	$166.30
Purchase #4	$76.27	13.634%	$86.6687	$86.67	$86.65	$86.70
Purchase #5	$205.46	12.228%	$230.5836	$230.58	$230.60	$230.60
Purchase #6	$215.65	10.617%	$238.5456	$238.55	$238.55	$238.50
Purchase #7	$144.55	8.330%	$156.591	$156.59	$156.60	$156.60
7 purchase totals =	$947.13		$1,046.3402	$1,046.34	$1,046.30	$1,046.30