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	$182.78	7.524%	$196.5324	$196.53	$196.55	$196.50
Purchase #2	$199.77	4.415%	$208.5898	$208.59	$208.60	$208.60
Purchase #3	$175.47	3.336%	$181.3237	$181.32	$181.30	$181.30
Purchase #4	$44.97	6.409%	$47.8521	$47.85	$47.85	$47.90
Purchase #5	$109.90	9.481%	$120.3196	$120.32	$120.30	$120.30
Purchase #6	$123.75	12.400%	$139.095	$139.10	$139.10	$139.10
Purchase #7	$181.49	12.693%	$204.5265	$204.53	$204.55	$204.50
7 purchase totals =	$1,018.13		$1,098.2391	$1,098.24	$1,098.25	$1,098.20