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	$96.83	12.436%	$108.8718	$108.87	$108.85	$108.90
Purchase #2	$168.42	3.523%	$174.3534	$174.35	$174.35	$174.40
Purchase #3	$54.95	12.786%	$61.9759	$61.98	$62.00	$62.00
Purchase #4	$240.59	12.815%	$271.4216	$271.42	$271.40	$271.40
Purchase #5	$33.61	13.812%	$38.2522	$38.25	$38.25	$38.30
Purchase #6	$106.25	10.818%	$117.7441	$117.74	$117.75	$117.70
Purchase #7	$240.48	6.380%	$255.8226	$255.82	$255.80	$255.80
7 purchase totals =	$941.13		$1,028.4416	$1,028.43	$1,028.40	$1,028.50