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	$115.61	13.667%	$131.4104	$131.41	$131.40	$131.40
Purchase #2	$116.33	9.467%	$127.343	$127.34	$127.35	$127.30
Purchase #3	$162.79	7.509%	$175.0139	$175.01	$175.00	$175.00
Purchase #4	$148.52	3.819%	$154.192	$154.19	$154.20	$154.20
Purchase #5	$220.81	11.152%	$245.4347	$245.43	$245.45	$245.40
Purchase #6	$196.57	3.682%	$203.8077	$203.81	$203.80	$203.80
Purchase #7	$205.62	6.815%	$219.633	$219.63	$219.65	$219.60
7 purchase totals =	$1,166.25		$1,256.8347	$1,256.82	$1,256.85	$1,256.70