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	$64.75	12.504%	$72.8463	$72.85	$72.85	$72.80
Purchase #2	$70.47	11.686%	$78.7051	$78.71	$78.70	$78.70
Purchase #3	$245.80	7.362%	$263.8958	$263.90	$263.90	$263.90
Purchase #4	$95.91	8.397%	$103.9636	$103.96	$103.95	$104.00
Purchase #5	$225.38	13.382%	$255.5404	$255.54	$255.55	$255.50
Purchase #6	$36.27	13.739%	$41.2531	$41.25	$41.25	$41.30
Purchase #7	$196.95	12.843%	$222.2443	$222.24	$222.25	$222.20
7 purchase totals =	$935.53		$1,038.4486	$1,038.45	$1,038.45	$1,038.40