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	$238.49	9.747%	$261.7356	$261.74	$261.75	$261.70
Purchase #2	$161.99	5.727%	$171.2672	$171.27	$171.25	$171.30
Purchase #3	$88.28	9.868%	$96.9915	$96.99	$97.00	$97.00
Purchase #4	$137.97	3.601%	$142.9383	$142.94	$142.95	$142.90
Purchase #5	$238.51	7.177%	$255.6279	$255.63	$255.65	$255.60
Purchase #6	$136.94	4.337%	$142.8791	$142.88	$142.90	$142.90
Purchase #7	$37.84	6.743%	$40.3916	$40.39	$40.40	$40.40
7 purchase totals =	$1,040.02		$1,111.8312	$1,111.84	$1,111.90	$1,111.80