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	$54.68	11.206%	$60.8074	$60.81	$60.80	$60.80
Purchase #2	$92.88	3.726%	$96.3407	$96.34	$96.35	$96.30
Purchase #3	$203.25	10.702%	$225.0018	$225.00	$225.00	$225.00
Purchase #4	$235.91	9.751%	$258.9136	$258.91	$258.90	$258.90
Purchase #5	$228.72	11.802%	$255.7135	$255.71	$255.70	$255.70
Purchase #6	$144.89	5.835%	$153.3443	$153.34	$153.35	$153.30
Purchase #7	$117.68	11.686%	$131.4321	$131.43	$131.45	$131.40
7 purchase totals =	$1,078.01		$1,181.5534	$1,181.54	$1,181.55	$1,181.40